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What is cos() in C?

harris910

The cos() function returns the cosine of a number. To be more specific, it returns the cosine of a number in the radian float value.

Figure 1 shows the mathematical representation of the cos() function.

Figure 1: Mathematical representation of cosine function

Note:

  • The math.h header file is required for this function.
  • This cos() function only works for right-angled triangles.

Syntax

double cos(double num)

Parameter

This function requires a number that represents an angle in radians as a parameter.

In order to convert degrees to radians, use the following formula:

radians = degrees * ( PI / 180.0 )

Return value

cos() returns the cosine of a number (radians float value) that is sent as a parameter.

Example

#include<stdio.h>
//header file
#include<math.h>

int main() {
    //positive number in radians
    printf("The cosine of %lf is %lf \n", 2.3, cos(2.3));

    // negative number in radians
    printf("The cosine of %lf is %lf \n", -2.3, cos(-2.3));

    //converting the degrees angle into radians and then applying cos()
    // degrees = 90.0
    // PI = 3.14159265
    // result first converts degrees to radians then apply cos
    double result=cos(90.0 * (3.14159265 / 180.0));
    printf("The cosine of %lf is %lf \n", 90.0, result);


}

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