cos

cos

Compute the Trigonometric Cosine

Portability: ISO/ANSI C conforming, UNIX compatible

SYNOPSIS
DESCRIPTION
RETURN VALUE
DIAGNOSTICS
EXAMPLE
RELATED FUNCTIONS
SEE ALSO

SYNOPSIS

#include <math.h>

double cos(double x);

DESCRIPTION

cos computes the trigonometric cosine of the value x . The cos function expects a value of x expressed in radians.

Because the cosine function is periodic, only the value of x mod 2 [pi] is used to compute the cosine. If x is very large, only a limited precision is left to represent x mod 2 [pi] . Thus, an error message is written for very large negative or positive arguments (see DIAGNOSTICS below).

RETURN VALUE

cos returns the value of the cosine of the argument x , provided that this value is defined and computable. The return value is of type double .

DIAGNOSTICS

For a very large argument ( x > 6.7465e9), the function returns 0.0. In this case, the message "total loss of significance" is also written to stderr (the standard error file).

If an error occurs in cos , the _matherr routine is called. You can supply your own version of _matherr to suppress the diagnostic message or modify the value returned.

EXAMPLE

This example computes the cosine of a 60-degree angle using cos :

#include <stdio.h>
#include <lcmath.h>

main()
{
   double y;

      /* The constant M_PI is declared in the  */
      /*  header file . 60 degrees   */
      /*  is pi/3 radians.                     */
   y = cos(M_PI/3);

   printf("cos(%f) =  %f\n",M_PI,y);
}

RELATED FUNCTIONS

sin , tan , _matherr

SEE ALSO

Mathematical Functions

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