cos

Cosine function

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Contents

Interface
Description
Special Values
See Also
Standards
Page Comments

Interface

#include <math.h>double  cos (double x)
long  cosl (long double x)
float  cosf (float x)

#include <complex.h>double complex  ccos (double complex z)
long double complex  ccosl (long double complex z)
float complex  ccosf (float complex z)

Description

The cos function computes the cosine of x (measured in radians). It returns a value in the range of -1 to 1.

The complex cosine is defined by

$\cos(x) = \frac{\exp(i x)+\exp(-i x)}{2 i}$

(1)

Example:

Example - Cosine function

Workings

#include <stdio.h>
#include <math.h>
int main()
{
  double x = 1.047198;
  double result = cos(x);
  printf("The cosine of %lf is %lf\n", x, result);
  return 0;
}

Solution

Output:

The cosine of 1.047198 is 0.500000

Special Values

cos ( 0 ) returns 1.

cos ( ∞ ) returns a NaN and raises the invalid floating-point exception.

Standards

The cos function conforms to ISO/IEC 9899:1999(E).

Page Comments

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double	`cos` (double x)
long	`cosl` (long double x)
float	`cosf` (float x)

double complex	`ccos` (double complex z)
long double complex	`ccosl` (long double complex z)
float complex	`ccosf` (float complex z)