sin : <math.h> library function

The function double sin(double x); returns the sine of x, expressed in radians.

Function prototype of sin

double sin(double x);
  • x : A floating point value representing an angle in radians.

Return value of sin

It returns the sine of x.

C program to show the use of sin function

The following program shows the use of sin function to calculate sine of an angle.

#include <stdio.h>
#include <math.h>

#define PI 3.14159

int main(){
    double value, radian, degree;
    printf("Enter an angle in degree\n");
    scanf("%lf", &degree);
    
    /* 
     *  Degree to radian conversion
     *  One degree is equal to PI/180 radians.
     *  Where PI = 22/7 = 3.14159(approx)
     */
    radian = degree * (PI/180.0);
    value = sin(radian);
    
    printf("The sine of %lf is %lf\n", degree, value);
        
    return 0;
}

Program Output
Enter an angle in degree
30
The sine of 30.000000 is 0.500000
Enter an angle in degree
90
The sine of 90.000000 is 1.000000