# std::cos(std::complex) (3) - Linux Manuals

## NAME

std::cos(std::complex) - std::cos(std::complex)

## Synopsis

template< class T >
complex<T> cos( const complex<T>& z );

Computes complex cosine of a complex value z.

## Parameters

z - complex value

## Return value

If no errors occur, the complex cosine of z is returned.
Errors and special cases are handled as if the operation is implemented by std::cosh(i*z), where i is the imaginary unit.

## Notes

The cosine is an entire function on the complex plane, and has no branch cuts.
Mathematical definition of the cosine is cos z =

eiz
+e-iz
2

## Example

// Run this code

#include <iostream>
#include <cmath>
#include <complex>

int main()
{
std::cout << std::fixed;
std::complex<double> z(1, 0); // behaves like real cosine along the real line
std::cout << "cos" << z << " = " << std::cos(z)
<< " ( cos(1) = " << std::cos(1) << ")\n";

std::complex<double> z2(0, 1); // behaves like real cosh along the imaginary line
std::cout << "cos" << z2 << " = " << std::cos(z2)
<< " (cosh(1) = " << std::cosh(1) << ")\n";
}

## Output:

cos(1.000000,0.000000) = (0.540302,-0.000000) ( cos(1) = 0.540302)
cos(0.000000,1.000000) = (1.543081,-0.000000) (cosh(1) = 1.543081)

computes sine of a complex number (sin(z))
sin(std::complex) (function template)
computes tangent of a complex number (tan(z))
tan(std::complex) (function template)

acos(std::complex) computes arc cosine of a complex number (arccos(z))
(function template)
(C++11)

cos
cosf
cosl computes cosine (cos(x))
(function)

(C++11)
(C++11)
applies the function std::cos to each element of valarray
cos(std::valarray) (function template)