It calculates the area of any equilateral triangle with the given length of the side.

#include <stdio.h>
#include <math.h> // for sqrt() function
 
int main()
{
    float length, area;
    printf("Enter the length of a single side on the triangle:\n ");
    scanf("%f", &length);
 
    area = (sqrt(3) / 4) * (length* length);// calculates the area
 
    printf("Area of the equilateral triangle :  %f sq.units", area);
 
    return 0;
} 

Enter the length of a single side on the triangle: 5
Area of the equilateral triangle :  10.825317 sq.units