std::cos

 

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Defined in header <cmath>
float       cos( float arg );
double      cos( double arg );
long double cos( long double arg );
double      cos( Integral arg );		(since C++11)

Computes the cosine of arg.

Parameters

arg

-

value representing angle in radians, of a floating-point or Integral type

Return value

Cosine of arg in the range [-1.0 ; 1.0].

The result may have little or no significance if the magnitude of arg is large

(until C++11)

Exceptions

Errors are reported as specified in math_errhandling

If the implementation supports IEEE floating-point arithmetic (IEC 60559),

• if the argument is ±0, the result is 1.0
• if the argument is ±∞, NaN is returned and FE_INVALID is raised
• if the argument is NaN, NaN is returned

Notes

The case where the argument is infinite is not specified to be a domain error in C, but it is defined as a domain error in POSIX

Example

Run this code

#include <iostream>
#include <cmath>
#include <cerrno>
#include <cfenv>
 
#pragma STDC FENV_ACCESS ON
const double pi = std::acos(-1);
int main()
{
    // typical usage
    std::cout << "cos(pi/3) = " << std::cos(pi/3) << '\n'
              << "cos(pi/2) = " << std::cos(pi/2) << '\n'
              << "cos(-3*pi/4) = " << std::cos(-3*pi/4) << '\n';
    // special values
    std::cout << "cos(+0) = " << std::cos(0.0) << '\n'
              << "cos(-0) = " << std::cos(-0.0) << '\n';
    // error handling 
    std::feclearexcept(FE_ALL_EXCEPT);
    std::cout << "cos(INFINITY) = " << std::cos(INFINITY) << '\n';
    if(std::fetestexcept(FE_INVALID)) std::cout << "    FE_INVALID raised\n";
}

Possible output:

cos(pi/3) = 0.5
cos(pi/2) = 6.12323e-17
cos(-3*pi/4) = -0.707107
cos(+0) = 1
cos(-0) = 1
cos(INFINITY) = -nan
    FE_INVALID raised

See also

sinsinfsinl (C++11)(C++11)	computes sine (\({\small\sin{x}}\)sin(x)) (function)
tantanftanl (C++11)(C++11)	computes tangent (\({\small\tan{x}}\)tan(x)) (function)
acosacosfacosl (C++11)(C++11)	computes arc cosine (\({\small\arccos{x}}\)arccos(x)) (function)
cos(std::complex)	computes cosine of a complex number (\({\small\cos{z}}\)cos(z)) (function template)
cos(std::valarray)	applies the function std::cos to each element of valarray (function template)
C documentation for cos