刻在等边三角形上的圆的面积

给定这里是边长为a的等边三角形，任务是找到该等边三角形内切圆的面积。
例子：

Input : a = 4
Output : 4.1887902047863905

Input : a = 10
Output : 26.1799387799

方法：

Area of equilateral triangle = 

Semi perimeter of equilateral triangle = (a + a + a) / 2
Radius of inscribed circle r = Area of equilateral triangle / Semi perimeter of equilateral triangle 
                                            = 

                                            = 

Area of circle = PI*(r*r) = 

下面是上述方法的实现：

C++

*** QuickLaTeX cannot compile formula:
 

*** Error message:
Error: Nothing to show, formula is empty

Java

*** QuickLaTeX cannot compile formula:
 

*** Error message:
Error: Nothing to show, formula is empty

Python3

*** QuickLaTeX cannot compile formula:
 

*** Error message:
Error: Nothing to show, formula is empty

C#

*** QuickLaTeX cannot compile formula:
 

*** Error message:
Error: Nothing to show, formula is empty

PHP

// C++ program to find the area
// of circle which is inscribed
// in equilateral triangle
# include
# define PI 3.14
using namespace std;
 
// Function return the area of circle
// inscribed in equilateral triangle
float circle_inscribed(int a)
{
    return PI * (a * a) / 12;
}
 
// Driver code
int main()
{
    int a = 4;
 
    cout << circle_inscribed(a);
    return 0;
}
 
// This code is contributed
// by Mahadev99

Javascript

// Java program to find the area
// of circle which is inscribed
// in equilateral triangle
import java.io.*;
 
class GFG
{
 
static double PI = 3.14;
 
// Function return the area of circle
// inscribed in equilateral triangle
static double circle_inscribed(int a)
{
    return PI * (a * a) / 12;
}
 
// Driver code
public static void main (String[] args)
{
    int a = 4;
 
    System.out.println(circle_inscribed(a));
}
}
 
// This code is contributed by anuj_67

输出：

# Python3 program to find the area of circle
# which is inscribed in equilateral triangle
 
# import math library for pi value
from math import pi
 
# Function return the area of circle
# inscribed in equilateral triangle
def circle_inscribed(a):
    return pi*(a * a) / 12
 
# Driver code
a = 4
print(circle_inscribed(a))