cos, cosf, cosl

Parameters

Return value

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

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

#include <errno.h>
#include <fenv.h>
#include <math.h>
#include <stdio.h>
 
#ifndef __GNUC__
#pragma STDC FENV_ACCESS ON
#endif
 
int main(void)
{
    const double pi = acos(-1);
 
    // typical usage
    printf("cos(pi/3) = %f\n", cos(pi / 3));
    printf("cos(pi/2) = %f\n", cos(pi / 2));
    printf("cos(-3*pi/4) = %f\n", cos(-3 * pi / 4));
 
    // special values
    printf("cos(+0) = %f\n", cos(0.0));
    printf("cos(-0) = %f\n", cos(-0.0));
 
    // error handling
    feclearexcept(FE_ALL_EXCEPT);
    printf("cos(INFINITY) = %f\n", cos(INFINITY));
    if (fetestexcept(FE_INVALID))
        puts("    FE_INVALID raised");
}

cos(pi/3) = 0.500000
cos(pi/2) = 0.000000
cos(-3*pi/4) = -0.707107
cos(+0) = 1.000000
cos(-0) = 1.000000
cos(INFINITY) = -nan
    FE_INVALID raised

References

See also