# Program to calculate area of Enneagon

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An enneagon also known as nonagon is a polygon with 9 sides. To calculate the area of enneagon the following formula is used,

Area of ennagon = ((a2*9) / 4*tan (20°)) ∼= (6.18 * a2)

Code Logic, The area of a polygon with nine sides is calculated by using the formula, ((a2*9) / 4*tan (20°)) ∼= (6.18 * a2). The value 6.18 is filled into a float variable called multiplier, this value then multiplied by the square of side of enneagon.

## Example

Live Demo

#include <stdio.h>
#include <math.h>
int main(){
int a = 6;
float area;
float multiplier = 6.18;
printf("Program to find area of Enneagon \n");
printf("The side of the Enneagon is %d \n", a);
area = (6.18 * a * a);
printf("The area of Enneagon is %f \n", area);
return 0;
}

## Output

Program to find area of Enneagon
The side of the Enneagon is 6
The area of Enneagon is 222.479996