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# cos

Cosine function
View other versions (4)

## 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

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).