A note to finger the Print to posture in the swatch,
what is the wrap ping should the not sound be math,
as arithmetic seeks & words just verse,
is the sing of monotone a desperate switch?
Sort did off description of noun verses noise,
the echo land to communicate soy,
milk in nature texture be cottage's wheel,
thicken that adding only exit to speak!!
Nostrodamus had an Affinity with bulb bust?,
cycle a challenge and pear a graph the apple,
banana the grape touch thorn with a needle?,
shy are the venue's of virtues a pawn Earth.
Chest piece while check err's gallant Gallon's at quartz,
is it the field of where is that sand?,
or is soil so fertile thus country's in town,
sit deed is promise of more than a found!!
A fingerprint Palm with sweeping Winds create soared,
across that is the void of that plaza each inch is it's bound?,
Pandora must blush as the rouge is in cheeks,
smiling difference while work is in tiled.
The Rule of Thumb,
a golden rule,
book of owe mass stir is church in the pew,
Bankers and in Cents,
a penny of leant east favor of south,
what than is paw should the cat say it cloak?
Virtue signalling
From Wikipedia, the free encyclopedia
Virtue signalling is the conspicuous expression of
moral values done primarily with the intent of enhancing
standing within a social group.
[1] The term was first used in
signalling theory, to describe any behavior that could be used to signal
virtue—especially
piety among the religious.
[2] In recent years, the term has become more commonly used as a
pejorative characterization by commentators to criticize what they regard as empty, or superficial support of certain political views, and also used within groups to criticize their own members for valuing outward appearance over substantive action.
[3][4] This usage of the term has been criticized for misusing the concept of signalling and encouraging lazy thinking.
[5] Within signalling theory[edit]
Similarly,
signalling is considered within economics. A bank's impressive architecture may serve as a signal of its financial soundness, since a less well-endowed bank could only afford less impressive buildings. Qualifications can signal a person's ability to an employer, even when those qualifications are not strictly necessary, since a less able job applicant will not be able to achieve the same level of qualification.
[5]Unless signalling is considered, costly religious rituals such as
circumcision,
fasting, and
snake handling look paradoxical in both evolutionary and economic terms. Religion may have arisen to increase and maintain intragroup cooperation,
[6] and religious traditions include costly rituals, performed publicly, as a hard-to-fake sign of commitment.
[7] Such behavior is sometimes described as "virtue signalling".
[2]Pejorative usage[edit]
In the late 2000s, the term began to be redefined on internet forums and social media away from its academic meaning and turned into a pejorative.
[citation needed] Examples of behavior described as virtue signalling include changing Facebook profile pictures to support a cause, participation in the
Ice Bucket Challenge, offering
thoughts and prayers after a tragedy, celebrity speeches during
award shows, politicians pandering to constituents on ideological issues, and others.
[4]According to linguist
Geoffrey Nunberg, the term is more common among the
political right. Lexographer
Orin Hargraves says that the term stems from
social media, which removes barriers to broadcasting sentiments. Hargrave links the term to the "-shaming" category of neologisms, such as "prayer-shaming", which can have an opposite meaning to virtue signalling.
Merriam-Webster editor Emily Brewster described it as an academic-sounding counterpart to "humblebrag," a term coined by
Harris Wittels in 2010.
[4]The blog
LessWrong discussed the underlying concept as early as February 2009.
[8][9]On June 22, 2014, a comment posted on a
PJ Media article used the term "Virtue Signalling" to describe several articles critical of a piece by
George Will about the US Federal government's reactions to claims of on-campus rape.
[10][11]In April 2015, writing in
The Spectator, British author
James Bartholomew used the term to describe public, empty gestures intended to convey socially approved attitude without any associated risk or sacrifice.
[12] Bartholomew specifically criticized in-store advertising at
Whole Foods Market where a picture of a mother carrying her child on her shoulders under the caption "VALUES MATTER...We are part of a growing consciousness that is bigger than food—one that champions what's good."
[13][14][15] He stated that "This a particularly blatant example of the increasingly common phenomenon of what might be called 'virtue signalling'—indicating that you are kind, decent and virtuous."
[13] He also applied the phrase to several other media, academic, and political figures.
[13] According to Bartholomew, virtue signalling can be either declarations of support, or declarations of hate towards negative things, as a way to hide self-aggrandizing intentions of the signal.
[16][12][3]In a later article, Bartholomew incorrectly claimed to have invented the phrase.
[17] Bartholomew's claims have been challenged by
The Boston Globe[4] and
The Guardian, although both credited Bartholomew with popularizing the term.
[3]In a blog post for the
Adam Smith Institute,
Sam Bowman stated that the meaning of the term popularised by James Bartholomew misuses the concept of signalling and encourages lazy thinking.
[5] In
The Guardian,
Zoe Williams described the phrase as the "sequel insult to
champagne socialist",
[18] while fellow
Guardian writer David Shariatmadari says that while the term serves a purpose, its overuse as an
ad hominem attack during political debate has rendered it a meaningless political
buzzword.
[3] In an article later published by the
New Statesman,
Tanya Gold claimed that 'people who accuse others of "virtue signalling" are trying to stigmatise empathy', describing it as 'devious political propaganda'.
[19]Helen Lewis, writing for the
New Statesman, blamed virtue signalling for the
Labour Party's defeat in the
2015 general election, suggesting that the desire to be seen as holding virtuous opinions leads political activists to focus on issues such as
nuclear disarmament that are lofty and remote to common voters, resulting in an
echo chamber effect that led Labour strategists to underestimate support for Conservative policies.
[20]

1.0E. Language and script of the description
When applicable, apply these guidelines, including the use of brackets, to headings.
Table of Contents:
Do not attempt to replicate font features such as bold and italic (e.g., when used to indicate a scientific name) through the use of underlining or other means of indicating such features.
Pre-Modern Forms of Letters:
In general, transcribe letters as they appear in the source. However, convert earlier forms of letters and earlier forms of diacritical marks into their modern form, as specified herein. If there is any doubt as to the correct conversion of elements to modern forms, transcribe them from the source as exactly as possible. (See also the section on
Special Letters, Diacritical Marks, and Punctuation Marks.)
The following represent a special case: u/v, uu, or vv/w. When these letters are used in Latin and some other languages without regard to their vocalic or consonantal value, so that "u" is used for a "v," etc., the transcription should be regularized. This means that for the bibliographic description of items published after 1800,
1. use v for consonants, e.g., vox, Victoria;
2. use u for vowels, e.g., uva, Ursa Major;
3. use w for consonantal uu or vv, e.g., Windelia.
Follow this guide also for publications of any date when the case is not one of bibliographic description, e.g., headings or citations from reference works.
The letters i/j should be handled differently. For the bibliographic descriptions of items published after 1800, transcribe "i" and "j" as they appear; do not attempt any regularization. PCC practice: Follow this stipulation also for uniform titles for series.
For any other case of headings, citations from reference sources, etc.,
1. use j for consonants, e.g., jus, Julius;
2. use i for vowels, e.g., iter, Ilias.
N.B. For the transcription of any of these letters in bibliographic description for pre-1801 publications, apply
Descriptive Cataloging of Rare Materials (Books) (DCRM(B)). For the use of uniform titles, so that DCRM(B) titles file properly (i.e., together with the titles of post-1800 publications), see
LCRI 25.1.
Matter That Cannot Be Reproduced by the Facilities Available The rule, in effect, requires as much fidelity to the source as the technical capacity within the cataloging agency will allow. It recommends a "cataloguer’s description in square brackets" for any "matter that cannot be reproduced by the facilities available." Generally, this is a practicable solution, but there are special instances in which doing other than describing the matter is appropriate. The main purposes of these instructions are to categorize all the methods to be employed, including a "cataloguer’s description," and to give specific directions for each in terms of the particular character set phenomenon encountered.
In the context of machine-readable catalog records note that as used in 1.0E and in the preceding paragraph, "facilities available" means the totality of characters that can be represented in machine-readable form and displayed/printed (known as the "MARC-8 character set"; referred to hereafter as the "character set"). These characters can also be represented in the UCS/Unicode UTF-8 character set, but the guidelines in this LCRIapply only to that subset of the Unicode UTF-8 set that has a counterpart in MARC-8, i.e., the MARC repertoire of UTF-8. Conventions appropriate to particular character set situations have been developed as follows:
Apply the appropriate conventions described in the sections below. As judged appropriate, use notes to explain and added entries to provide additional access. In the special provisions below, notes are suggested as possible models for form, not to require the use of the note.
Super/Subscript Characters If the super/subscript placement of a character is not essential to avoid serious distortion or loss of intelligibility (e.g.,

,

,

), record the super/subscript character on the line in the regular manner (e.g., no., 2e). If a period is associated with the super/subscript letter (e.g.,

) and the characters are the abbreviation of a single word, record the period as the last element (e.g., Ma.). In case of serious distortion or loss of intelligibility, record the character in super/subscript position for all such characters available in the character set, namely, Arabic numerals (0-9), the minus sign (
- ), parentheses (
( ) ), and the plus sign (
+ ). In all other cases use the double underscore convention described in the section on
Special Letters, Diacritical Marks, and Punctuation Marks. Give the letter being represented in upper or lower case according to the source.

In roman script records romanize all occurrences of Greek letters (with the exception below) regardless of the facilities available (the intent is to assist filing and searching even though there are characters for alpha, beta, and gamma in the character set and certain Greek capital letters are identical to their roman equivalents). If the context shows that a Greek letter or letters is used to represent a letter in the International Phonetic Alphabet, however, see the section on
Special Letters, Diacritical Marks, and Punctuation Marks.
Exception: If the Greek letter appears separately, give the name of the letter in the language of the context (if unknown in the language of the context, use English) enclosed within brackets. For searching purposes, insure that the bracketed interpolation is not connected with other letters. Thus, if no space appears in the source on either side of the Greek letter, put a space on either side of the bracketed interpolation, except when this interpolation is already distinct from adjacent letters by the presence of characters that serve as separators. N.B. This provision is necessary, because brackets do not serve as separators for searching purposes. ( )
When a Greek letter is used in a word that is otherwise in the roman alphabet in the source, use the romanized form of the letter (instead of its name) in brackets.
Special Marks of Contraction When special marks of contraction have been used by the printer in continuance of the manuscript tradition, expand affected words to their full form, enclosing supplied letters within brackets.
Do not expand conventional abbreviations in which a period follows a letter or letters. However, when an abbreviation standing for an entire word appears in the source, record instead the word itself, enclosing it in brackets, e.g., "... amico[rum] [et] ..." When the meaning of an abbreviation or contraction cannot be determined, substitute a question mark within brackets for each element in question, e.g., "... amico[?] [?] ..." When the meaning of an abbreviation or contraction is conjectural, use the question mark after the supplied letters or word within the same set of brackets, e.g., "...amico[rum?] ..."
When titles are "expanded," title added entries may be generated by the first indicator in the
245 field . The added entry will be exactly the same as the title proper (including the brackets around letters). To express a title added entry in any other form, use a
246 field .
246 3# $a Breviarium monasticum secundum ritum et morem monachorum Ordinis Sancti Benedicti de observantia Casinensis Congregationis
Special Letters, Diacritical Marks, and Punctuation Marks Use the double underscore (

) as the conventional means of signaling special letters (including superscript and subscript letters), diacritical marks, and punctuation marks for which there is no exact representation in the character set. Use the double underscore with the nearest roman equivalent in cases in which the roman equivalent is obvious, e.g.,

. When the nearest roman equivalent is not obvious or there is doubt that it is obvious, it is necessary to establish the equivalent, after which the list of equivalencies will be updated. The equivalencies below have been established to date, mostly from the International Phonetic Alphabet (IPA). Note that the IPA uses some Greek letters; when it is judged by the context (usually some form of linguistic study) that the Greek letter probably derives from its use in the IPA, use the double underscore convention or the
equivalency indicated below, not the convention for Greek letters given above.

Note that the use of the double underscore convention does not always insure a one-for-one equivalency; the intent, instead, is to signal those cases in which the character used in the catalog record is not an exact replication of the character in the source.
Exception: Do not use the double underscore convention in the following cases; use instead the equivalent indicated:
The objective in treating signs and symbols not represented in the character set is to render or convey the intention without undue time and effort and with a minimum of interpolation, using one of the techniques described in this section. Note that a minimum of interpolation is wanted because those searching the machine catalog cannot very often be expected to "second-guess" the cataloger in this respect, i.e., users will normally formulate search queries that necessarily do not take interpolations into account. As judged appropriate, use notes to explain and added entries to provide additional access; the examples below are illustrative, not prescriptive.
1. If the symbol is judged not to be a integral or essential part of the title, do not intervene in the transcription. Instead, omit the symbol; explain its presence in a note if it is judged worth mentioning.
transcription: 245 10 $a "W" today! Tomorrow?
(On the title page the traditional female symbol appears under the letter "W" but the preface makes it clear that the symbol is not intended to form part of the title and gives the full title.)
suggested note: 500 ## $a On t.p. the symbol for female appears under the letter "W"
added entry: 246 30 $a Women today! Tomorrow?
2. Use existing characters when this can be done without serious distortion or loss of intelligibility.
4. Substitute in the language of the context the word, phrase, etc., that is the obvious spoken/written equivalent (if unknown in the language of the context, use English); bracket the interpolated equivalent. If the element in the source is not preceded or followed by a space, in general precede or follow the bracketed interpolation by a space unless the preceding or following character in the source is itself also a separator or unless the use of a space would create an unintended result for searching.
chief source: I

a piano
transcription: 245 10 $a I [love] a piano
suggested note: 500 ## $a On t.p. "[love]" appears as a heart
chief source: A study of the

transcription: 245 12 $a A study of the [ankh]
suggested note: 500 ## $a On t.p. "[ankh]" appears as the ankh symbol
chief source: Poe

and free verse
transcription: 245 10 $a Poe[try] and free verse
(The interpolation is not preceded by a space because that would create two words for searching (brackets are not separators).)
suggested note: 500 ## $a On t.p. "[try]" appears as an illustration in the form of a tree
chief source: Tinglysningslovens §38
transcription: 245 10 $a Tinglysningslovens [paragraf] 38
chief source: Dokumentation der politischen Geschichte zur Reform des §144 STG
transcription: 245 10 $a Dokumentation der politischen Geschichte zur Reform des [Paragraphen] 144 STG
chief source: ... proposed rules governing §2255 proceedings ...
transcription: 245 10 $a ... $b ... proposed rules governing [section] 2255 proceedings ...
chief source: Roman Opalka : 16 Details aus dem Werk 1965/1-∞
transcription: 245 10 $a Roman Opalka : $b 16 Details aus dem Werk 1965/1-[unendlich]
suggested note: 500 ## $a On t.p. "[unendlich]" appears as the infinity symbol
chief source: Opalka 1965/1-∞ : 9 juin-9 juillet 1982
transcription: 245 10 $a Opalka 1965/1-[l'infinité] : $b 9 juin-9 juillet 1982
suggested note: 500 ## $a On t.p. "[l'infinité]" appears as the infinity symbol
chief source: The added mass coefficient of a cylinder oscillating in shallow water in the limit K→0 and K∞
transcription: 245 14 $a The added mass coefficient of a cylinder oscillating in shallow water in the limit K --> 0 and K [infinity]
(The arrow is input as two hyphens and an angle bracket.)
suggested note: 500 ## $a On t.p. "[infinity]" appears as the infinity symbol
Exception 1: Do not transcribe characters that indicate birth (e.g., an asterisk) or death (e.g., a dagger) even if such characters are in the character set. Do not use a mark of omission; instead, explain the omission in a note.
chief source: In honor of Saint Basil the Great

379
transcription: 245 10 $a In honor of Saint Basil the Great 379
suggested note: 500 ## $a On t.p. "379" is preceded by a dagger
chief source: Walter : *1926

1945 an der Ostfront
transcription: 245 00 $a Walter : $b 1926 1945 an der Ostfront
suggested note: 500 ## $a On t.p. "1926" is preceded by an asterisk; "1945" is preceded by an Iron Cross
Exception 2: Ignore symbols indicating trademark (registered or otherwise), patent, etc. These include a superscript or subscript "R" enclosed in a circle ( ® ) (ignore although included in the character set) and the superscript or subscript letters "TM" ( ä). Do not explain their presence in a note. (Ignore such symbols also when they appear with elements used in headings.)
chief source: The Gumby® books of letters
transcription: 245 14 $a The Gumby books of letters
If the spoken/written equivalent is not obvious or if there is doubt that it is obvious or if it is unknown, give an explanation or a description in the language of the context (if unknown in the language of the context, use English).
If a title consists solely of a sign or symbol or one or more marks of punctuation, provide an equivalent in all cases, even if the particular symbol is itself in the character set.
chief source: 
/ Gregory Corso
transcription: 245 10 $a [Ankh] / $c Gregory Corso
suggested note: 500 ## $a The title consists solely of the ankh symbol
chief source: + : [novellaciklus] / Czakó Gábor
transcription: 245 10 $a [Plusz : $b novellaciklus] / $c Czakó Gábor
("+" is in the character set.)
suggested note: 500 ## $a The title consists solely of a plus sign
chief source: © / Free Spirits, Inc.
transcription: 245 10 $a [Copyright] / $c Free Spirits, Inc.
("©" is in the character set.)
suggested note: 500 ## $a The title consists solely of the copyright symbol
chief source: ---- / Edvardas Gudavičius
transcription: 245 10 $a [Keturi brūkšniai] / $c Edvardas Gudavičius.
suggested note: 500 ## $a The title consists solely of four hyphens
but
chief source: ????? Steele's answers, by Daniel Steele ...
transcription: 245 10 $a ????? Steele's answers / $c by Daniel Steele ...
(Although the title begins with marks of punctuation, it also contains indexable data and no special intervention is required.)
See also:
Euler's formula
From Wikipedia, the free encyclopedia
This article is about Euler's formula in complex analysis. For Euler's formula in algebraic topology and polyhedral combinatorics, see
Euler characteristic.
| Part of a series of articles on the |
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Euler's formula is ubiquitous in mathematics, physics, and engineering. The physicist
Richard Feynman called the equation "our jewel" and "the most remarkable formula in mathematics".
[2]History[edit]

And since

the above equation tells us something about
complex logarithms by relating natural logarithms to imaginary (complex) numbers. Bernoulli, however, did not evaluate the integral.
Bernoulli's correspondence with Euler (who also knew the above equation) shows that Bernoulli did not fully understand
complex logarithms. Euler also suggested that the complex logarithms can have infinitely many values.

Cotes missed the fact that a complex logarithm can have infinitely many values, differing by multiples of 2iπ, due to the periodicity of the trigonometric functions.
Around 1740 Euler turned his attention to the exponential function instead of logarithms and obtained the formula used today that is named after him. It was published in 1748, obtained by comparing the series expansions of the exponential and trigonometric expressions.
[5][4]Applications in complex number theory[edit]
- Interpretation of the formula
The original proof is based on the
Taylor series expansions of the
exponential function ez (where
z is a complex number) and of
sin x and
cos x for real numbers
x (see below). In fact, the same proof shows that Euler's formula is even valid for all
complex numbers
x.
A point in the
complex plane can be represented by a complex number written in
cartesian coordinates. Euler's formula provides a means of conversion between cartesian coordinates and
polar coordinates. The polar form simplifies the mathematics when used in multiplication or powers of complex numbers. Any complex number
z = x + iy, and its complex conjugate,
z = x − iy, can be written as

where
- x = Re z is the real part,
- y = Im z is the imaginary part,
- r = |z| = √x2 + y2 is the magnitude of z
- φ = arg z = atan2(y, x).
φ is the
argument of
z, i.e., the angle between the
x axis and the vector
z measured counterclockwise in
radians, which is defined
up to addition of
2π. Many texts write
φ = tan−1 y/x instead of
φ = atan2(y,x), but the first equation needs adjustment when
x ≤ 0. This is because for any real
x and
y not both zero the angles of the vectors
(x, y) and
(−x, −y)differ by
π radians, but have the identical value of
tan φ = y/x.
- Use of the formula to define the logarithm of complex numbers
Now, taking this derived formula, we can use Euler's formula to define the
logarithm of a complex number. To do this, we also use the definition of the logarithm (as the inverse operator of exponentiation):

and that

both valid for any complex numbers a and b.
Therefore, one can write:

for any z ≠ 0. Taking the logarithm of both sides shows that

Finally, the other exponential law

Relationship to trigonometry[edit]

Relationship between sine, cosine and exponential function
Euler's formula provides a powerful connection between
analysis and
trigonometry, and provides an interpretation of the sine and cosine functions as
weighted sums of the exponential function:

The two equations above can be derived by adding or subtracting Euler's formulas:

and solving for either cosine or sine.
These formulas can even serve as the definition of the trigonometric functions for complex arguments x. For example, letting x = iy, we have:

Complex exponentials can simplify trigonometry, because they are easier to manipulate than their sinusoidal components. One technique is simply to convert sinusoids into equivalent expressions in terms of exponentials. After the manipulations, the simplified result is still real-valued. For example:

Another technique is to represent the sinusoids in terms of the
real part of a complex expression and perform the manipulations on the complex expression. For example:
![{\displaystyle {\begin{aligned}\cos(nx)&=\operatorname {Re} \left(e^{inx}\right)\\&=\operatorname {Re} \left(e^{i(n-1)x}\cdot e^{ix}\right)\\&=\operatorname {Re} {\Big (}e^{i(n-1)x}\cdot {\big (}\underbrace {e^{ix}+e^{-ix}} _{2\cos x}-e^{-ix}{\big )}{\Big )}\\&=\operatorname {Re} \left(e^{i(n-1)x}\cdot 2\cos x-e^{i(n-2)x}\right)\\&=\cos[(n-1)x]\cdot [2\cos(x)]-\cos[(n-2)x].\end{aligned}}}](https://wikimedia.org/api/rest_v1/media/math/render/svg/337400ddab1ffe801d4e8e73c86f7a9f446a79d4)
This formula is used for recursive generation of cos nx for integer values of n and arbitrary x (in radians).
Topological interpretation[edit]
Other applications[edit]
In
differential equations, the function
eix is often used to simplify solutions, even if the final answer is a real function involving sine and cosine. The reason for this is that the exponential function is the
eigenfunction of the operation of
differentiation.
In
electrical engineering,
signal processing, and similar fields, signals that vary periodically over time are often described as a combination of sinusoidal functions (see
Fourier analysis), and these are more conveniently expressed as the sum of exponential functions with
imaginary exponents, using Euler's formula. Also,
phasor analysis of circuits can include Euler's formula to represent the impedance of a capacitor or an inductor.

and the element is called a
versor in quaternions. The set of all versors forms a
3-sphere in the 4-space.
Definitions of complex exponentiation[edit]
The exponential function
ex for real values of
x may be defined in a few different equivalent ways (see
Characterizations of the exponential function). Several of these methods may be directly extended to give definitions of
ez for complex values of
z simply by substituting
z in place of
x and using the complex algebraic operations. In particular we may use either of the two following definitions, which are equivalent. From a more advanced perspective, each of these definitions may be interpreted as giving the unique
analytic continuation of
exto the complex plane.
Power series definition[edit]
For complex z

Limit definition[edit]
For complex z

Various proofs of the formula are possible.
Using power series[edit]

Using now the power-series definition from above, we see that for real values of x
![{\displaystyle {\begin{aligned}e^{ix}&=1+ix+{\frac {(ix)^{2}}{2!}}+{\frac {(ix)^{3}}{3!}}+{\frac {(ix)^{4}}{4!}}+{\frac {(ix)^{5}}{5!}}+{\frac {(ix)^{6}}{6!}}+{\frac {(ix)^{7}}{7!}}+{\frac {(ix)^{8}}{8!}}+\cdots \\[8pt]&=1+ix-{\frac {x^{2}}{2!}}-{\frac {ix^{3}}{3!}}+{\frac {x^{4}}{4!}}+{\frac {ix^{5}}{5!}}-{\frac {x^{6}}{6!}}-{\frac {ix^{7}}{7!}}+{\frac {x^{8}}{8!}}+\cdots \\[8pt]&=\left(1-{\frac {x^{2}}{2!}}+{\frac {x^{4}}{4!}}-{\frac {x^{6}}{6!}}+{\frac {x^{8}}{8!}}-\cdots \right)+i\left(x-{\frac {x^{3}}{3!}}+{\frac {x^{5}}{5!}}-{\frac {x^{7}}{7!}}+\cdots \right)\\[8pt]&=\cos x+i\sin x.\end{aligned}}}](https://wikimedia.org/api/rest_v1/media/math/render/svg/876f74f43699f5c15b79cb61fa3eec2dbb427837)
Using calculus[edit]
Another proof
[7] is based on the fact that all complex numbers can be expressed in polar coordinates. Therefore, for
some r and
θ depending on
x,

No assumptions are being made about r and θ; they will be determined in the course of the proof. From any of the definitions of the exponential function it can be shown that the derivative of eix is ieix. Therefore, differentiating both sides gives

Substituting r(cos θ + i sin θ) for eix and equating real and imaginary parts in this formula gives dr/dx = 0 and dθ/dx = 1. Thus, r is a constant, and θ is x + C for some constant C. The initial values r(0) = 1 and θ(0) = 0 come from e0i = 1, giving r = 1 and θ = x. This proves the formula
