**The Program in C++ to Calculate Area of an equilateral triangle is given below:**

```
#include<iostream>
using namespace std;
#include<math.h>
main(){
float s1;
float area;
cout<<" Hello, codeauri family,input the value of the side of the equilateral triangle here: ";
cin>>s1;
area = sqrt(3)/4*(s1*s1);
cout<<"well, the area of equilateral triangle is: "<<area<<endl;
cout << endl;
return 0;
}
```

## Output:

Hello, codeauri family,input the value of the side of the equilateral triangle here: 5

well, the area of equilateral triangle is: 10.8253

## Pro-Tips**💡**

This is a simple program written in C++ that calculates the area of an equilateral triangle.

The first line “#include<iostream>” allows the program to use input and output functions such as cout and cin.

The second line “using namespace std;” allows the program to use the standard library without having to qualify the names of functions.

The third line “#include<math.h>” allows the program to use the square root function, sqrt().

In the main function, two float variables are defined: s1 for the length of the side of the equilateral triangle, and area for the calculated area of the triangle.

The program prompts the user to input the value of the side of the triangle, and stores it in the variable s1.

The area is then calculated by using the formula (sqrt(3)/4*(s1*s1)) and the result is stored in the variable area.

The program then prints out the calculated area of the triangle. The last line “return 0;” indicates that the program has ended successfully.

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