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# What is acos() in C?

harris910

The acos() functionalso called the arc cosine function returns the inverse cosine of a number. To be more specific, it returns the inverse cosine of a number in radians.

Figure 1 shows the mathematical representation of the acos() function and Figure 2 shows the visual representation of the acos() function.

Figure 1: Mathematical representation of inverse cosine function
Figure 2: Visual representation of inverse cosine function

Note: The math.h header file is required for this function.

To convert radians to degrees, use the following formula.

degrees = radians * ( 180.0 / PI )


## Syntax

double acos(double num)


## Parameter

This function requires a number as a parameter. The parameter must be a double value between -1 and 1.

• -1 <= parameter <= 1

## Return value

acos() returns the inverse cosine of a number (radian double value) that is sent as a parameter. The return value lies in interval [0, pi] radians.

## Example

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

int main() {
printf("The arc cosine of %lf is %lf radians \n", 0.5, acos(0.5));

printf("The arc cosine of %lf is %lf radians \n", -0.5, acos(-0.5));

//applying acos() and then converting the result in radians to degrees
// PI = 3.14159265
double result=acos(0.5) * (180.0 / 3.14159265);
printf("The arc cosine of %lf is %lf degrees \n", 0.5, result);

}

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