NAME¶

std::cos,std::cosf,std::cosl - std::cos,std::cosf,std::cosl

Synopsis¶

Defined in header <cmath>
float cos ( float arg );
float cosf( float arg ); (since C++11)
double cos ( double arg ); (1) (2)
long double cos ( long double arg );
long double cosl( long double arg ); (3) (since C++11)
double cos ( IntegralType arg ); (4) (since C++11)

1-3) Computes the cosine of arg (measured in radians).
4) A set of overloads or a function template accepting an argument of any integral
type. Equivalent to 2) (the argument is cast to double).

Parameters¶

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

Return value¶

If no errors occur, the cosine of arg (cos(arg)) in the range [-1 ; +1], is
returned.

The result may have little or no significance if the magnitude of arg (until C++11)
is large

If a domain error occurs, an implementation-defined value is returned (NaN where
supported)

If a range error occurs due to underflow, the correct result (after rounding) is
returned.

Error handling¶

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¶

sin
sinf computes sine (\({\small\sin{x} }\)sin(x))
sinl (function)
(C++11)
(C++11)
tan
tanf computes tangent (\({\small\tan{x} }\)tan(x))
tanl (function)
(C++11)
(C++11)
acos
acosf computes arc cosine (\({\small\arccos{x} }\)arccos(x))
acosl (function)
(C++11)
(C++11)
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)