In this tutorial, you will learn how to **write a C program to calculate area of an equilateral triangle**. A triangle is called equilateral triangle if all three of its sides are equal.

**Formula to calculate area of an equilateral triangle:**

Area = (sqrt(3)/4 )* (side * side)

## C Program to calculate Area of an Equilateral triangle

The explanation of the program is available at the end of this program.

#include <stdio.h>

#include <math.h>

int main() {

float side, area;

// Prompt user for the side length

printf("Enter the side length of the equilateral triangle: ");

scanf("%f", &side);

// Calculate the area of equilateral triangle

area = (sqrt(3) / 4) * (side * side);

// print the area value after calculation

printf("Area of the equilateral triangle: %.2f\n", area);

return 0;

}

### Output:

Output 1:

Enter the side length of the equilateral triangle: 5

Area of the equilateral triangle: 10.83

Output 2:

Enter the side length of the equilateral triangle: 25

Area of the equilateral triangle: 270.51

### Explanation:

**Include Standard Libraries**:`#include <stdio.h>`

for standard input and output functions such as`printf`

and`scanf`

.`#include <math.h>`

The`sqrt`

function which we have used in the program is present in this library.

**Declare Variables**:`float side, area;`

The side variable is to hold the value of side of the equilateral triangle and area variable is to hold the area value after calculation.

**User Input**:`printf("Enter the side length of the equilateral triangle: ");`

prompts the user to enter the length of side of triangle.`scanf("%f", &side);`

reads the value entered by user and store it into the`side`

variable.

**Calculate Area**:`area = (sqrt(3) / 4) * (side * side);`

This formula is used for calculating the area.

**Print Result**:`printf("Area of the equilateral triangle: %.2f\n", area);`

prints the area of equilateral triangle with two decimal places.

**Return Statement**:`return 0;`

indicates that the program executed successfully.

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