Cot

Notations

Traditional name

Traditional notation

Mathematica StandardForm notation

Primary definition

Specific values

Specialized values

Values at fixed points

cot(((n π)/m)) can be expressed using only square roots if n∈ℤ and m is a product of a power of 2 and distinct Fermat primes {3, 5, 17, 257, …}.

Values at infinities

General characteristics

Domain and analyticity

cot(z) is an analytical function of z which is defined over the whole complex z-plane.

Symmetries and periodicities

Parity

cot(z) is an odd function.

Mirror symmetry

Periodicity

cot(z) is a periodic function with period π .

Poles and essential singularities

The function cot(z) has an infinite set of singular points:
a) z==π k/;k∈ℤ are the simple poles with residues 1;
b) z== (OverTilde[∞]) is an essential singular point.

Branch points

The function cot(z) does not have branch points.

Branch cuts

The function cot(z) does not have branch cuts.

Series representations

Generalized power series

Expansions at z==(Subscript[z, 0])

Expansions at z==0

Expansions at z==(π/2)

q-series

Dirichlet series

Asymptotic series expansions

Other series representations

Integral representations

On the real axis

Of the direct function

Limit representations

Continued fraction representations

Andreas Lauschke (2006)

Andreas Lauschke (2006)

A.Lauschke (2006)

A.Lauschke (2006)

Differential equations

Ordinary nonlinear differential equations

Transformations

Transformations and argument simplifications

Argument involving basic arithmetic operations

Argument involving inverse trigonometric and hyperbolic functions

Addition formulas

Half-angle formulas

Multiple arguments

Argument involving numeric multiples of variable

Argument involving symbolic multiples of variable

Products, sums, and powers of the direct function

Products of the direct function

Products involving the direct function

Sums of the direct function

Sums involving the direct function

Powers of the direct function

Sums of powers involving the direct function

Related transformations

Identities

Functional identities

Complex characteristics

Real part

Imaginary part

Absolute value

Argument

Conjugate value

Signum value

Differentiation

Low-order differentiation

Symbolic differentiation

Victor Adamchik (2005)

Fractional integro-differentiation

Integration

Indefinite integration

Involving only one direct function

Involving one direct function and elementary functions

Involving functions of the direct function

Involving functions of the direct function and a power function

Involving functions of the direct function and exponential function

Involving functions of the direct function, exponential and a power functions

Involving functions of the direct function and trigonometric functions

Involving functions of the direct function, trigonometric and a power functions

Involving functions of the direct function, trigonometric and exponential functions

Involving functions of the direct function, trigonometric, exponential and a power functions

Definite integration

For the direct function itself

Involving the direct function

Involving related functions

Summation

Finite summation

S. Fukuhara: New Trigonometric Identities and Generalized Dedekind Sums Tokyo Journal of Mathematics 26, 1-14 (2003)

Infinite summation

Products

Finite products

Representations through more general functions

Through hypergeometric functions

Brychkov Yu.A. (2005)

Through other functions

Involving Jacobi functions

Involving Mathieu functions

Involving some elliptic-type functions

Representations through equivalent functions

With inverse function

With related functions

Involving Exp

Involving Sin

Involving Cos

Involving Tan

Involving Csc

Involving Sec

Involving Sinh

Involving Cosh

Involving Tanh

Involving Coth

Involving Csch

Involving Sech

Involving trigonometric and hyperbolic functions

Inequalities

Zeros

Theorems

Hilbert cotangent transformation

(OverHat[f])(y)==(1/(2π))(∫_0^(2π))f(x) cot(((y-x)/2))dx⇔f(x)==(1/(2π))(∫_0^(2π))(OverHat[f])(y) cot(((y-x)/2))dy+(∫_0^(2π))f(x) dx.

Poisson formula

The value f(r (e^(i ϕ))) of an analytic function f(z) can be expressed through the values of f(z) along the circle r (e^(i ϑ)) by

f(r (e^(i ϕ)))==f(0)-(i/(2π))𝒫(∫_0^(2π))f(r (e^(i ϑ)))cot(((ϑ-ϕ)/2))dϑ.

Other information

Value properties

History

– E. Gunter (1620) used the notation "cotangent"
– J. Keill (1726)
– L. Euler (1748)

The function cot is encountered often in mathematics and the natural sciences.

Copyright