# Angle of intersection of two circles having their centers D distance apart

Given two positive integers **R1** and **R2** representing the radius of two intersecting circles having a distance **D** between their centers, the task is to find the cosine of the angle of intersection between the two circles.

**Examples:**

Input:R1 = 3, R2 = 4, D = 5Output:0

Input:R1 = 7, R2 = 3, D = 6Output:0.52381

**Approach:** The given problem can be solved by using the Geometric Algorithm as illustrated below:

From the above image and using the Pythagoras Theorem, the cosine of the angle of intersection of the two circles can be found using the formula:

Below is the implementation of the above approach:

## C++

`// C++ program for the above approach` `#include <bits/stdc++.h>` `using` `namespace` `std;` `// Function to find the cosine of the` `// angle of the intersection of two` `// circles with radius R1 and R2` `float` `angle(` `float` `R1, ` `float` `R2, ` `float` `D)` `{` ` ` `float` `ans = (R1 * R1 + R2 * R2 - D * D)` ` ` `/ (2 * R1 * R2);` ` ` `// Return the cosine of the angle` ` ` `return` `ans;` `}` `// Driver Code` `int` `main()` `{` ` ` `float` `R1 = 3, R2 = 4;` ` ` `float` `D = 5;` ` ` `cout << angle(R1, R2, D);` ` ` `return` `0;` `}` |

## Java

`// Java program for the above approach` `import` `java.io.*;` `class` `GFG{` ` ` `// Function to find the cosine of the` `// angle of the intersection of two` `// circles with radius R1 and R2` `static` `float` `angle(` `float` `R1, ` `float` `R2, ` `float` `D)` `{` ` ` `float` `ans = (R1 * R1 + R2 * R2 - D * D) /` ` ` `(` `2` `* R1 * R2);` ` ` ` ` `// Return the cosine of the angle` ` ` `return` `ans;` `}` `// Driver Code` `public` `static` `void` `main (String[] args)` `{` ` ` `float` `R1 = ` `3` `, R2 = ` `4` `;` ` ` `float` `D = ` `5` `;` ` ` ` ` `System.out.println(angle(R1, R2, D));` `}` `}` `// This code is contributed by Ankita saini` |

## Python3

`# Python3 program for the above approach` `# Function to find the cosine of the` `# angle of the intersection of two` `# circles with radius R1 and R2` `def` `angle(R1, R2, D):` ` ` ` ` `ans ` `=` `((R1 ` `*` `R1 ` `+` `R2 ` `*` `R2 ` `-` `D ` `*` `D) ` `/` ` ` `(` `2` `*` `R1 ` `*` `R2))` ` ` `# Return the cosine of the angle` ` ` `return` `ans` `# Driver Code` `if` `__name__ ` `=` `=` `'__main__'` `:` ` ` ` ` `R1 ` `=` `3` ` ` `R2 ` `=` `4` ` ` `D ` `=` `5` ` ` ` ` `print` `(angle(R1, R2, D))` ` ` `# This code is contributed by ipg2016107` |

## C#

`// C# program for the above approach` `using` `System;` `class` `GFG{` ` ` `// Function to find the cosine of the` `// angle of the intersection of two` `// circles with radius R1 and R2` `static` `float` `angle(` `float` `R1, ` `float` `R2, ` `float` `D)` `{` ` ` `float` `ans = (R1 * R1 + R2 * R2 - D * D) /` ` ` `(2 * R1 * R2);` ` ` ` ` `// Return the cosine of the angle` ` ` `return` `ans;` `}` `// Driver Code` `public` `static` `void` `Main(` `string` `[] args)` `{` ` ` `float` `R1 = 3, R2 = 4;` ` ` `float` `D = 5;` ` ` ` ` `Console.Write(angle(R1, R2, D));` `}` `}` `// This code is contributed by rutvik_56.` |

## Javascript

`<script>` `// Javascript program for the above approach ` `// Function to find the cosine of the` `// angle of the intersection of two` `// circles with radius R1 and R2` `function` `angle(R1, R2, D)` `{` ` ` `var` `ans = (R1 * R1 + R2 * R2 - D * D) /` ` ` `(2 * R1 * R2);` ` ` `// Return the cosine of the angle` ` ` `return` `ans;` `}` `// Driver Code` `var` `R1 = 3, R2 = 4;` `var` `D = 5;` `document.write(angle(R1, R2, D));` `// This code is contributed by Ankita saini` `</script>` |

**Output:**

0

**Time Complexity:** O(1)**Auxiliary Space:** O(1)