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Pi(π) in C++ with Examples
• Difficulty Level : Easy
• Last Updated : 18 Apr, 2020

In this article, we will discuss some of the mathematical function which is used to derived the value of Pi(π) in C++.

Method 1: Using acos() function:
Approach:

1. The value of Π is calculated using acos() function which returns a numeric value between [-Π, Π].
2. Since using acos(0.0) will return the value for Π/2. Therefore to get the value of Π:
```double pi = 2*acos(0.0);
```
3. Now the value obtained from above equation is estimated as:
```printf("%f\n", pi);
```

Below is the implementation of the above approach:

 `// C++ program for the above approach`` ` `#include "bits/stdc++.h"``using` `namespace` `std;`` ` `// Function that prints the``// value of pi``void` `printValueOfPi()``{`` ` `    ``// Find value of pi using``    ``// acos() function``    ``double` `pi = 2 * ``acos``(0.0);`` ` `    ``// Print value of pi``    ``printf``(``"%f\n"``, pi);``}`` ` `// Driver Code``int` `main()``{``    ``// Function that prints``    ``// the value of pi``    ``printValueOfPi();``    ``return` `0;``}`
Output:
```3.141593
```

Method 2: Using asin() function:
Approach:

1. The value of Π is calculated using asin() function which returns a numeric value between [-Π, Π].
2. Since using asin(1.0) will return the value for Π/2. Therefore to get the value of Π:
```double pi = 2*asin(1.0);
```
3. Now the value obtained from above equation is estimated as:
```printf("%f\n", pi);
```

Below is the implementation of the above approach:

 `// C++ program for the above approach`` ` `#include "bits/stdc++.h"``using` `namespace` `std;`` ` `// Function that prints the``// value of pi``void` `printValueOfPi()``{`` ` `    ``// Find value of pi using``    ``// asin() function``    ``double` `pi = 2 * ``asin``(1.0);`` ` `    ``// Print value of pi``    ``printf``(``"%f\n"``, pi);``}`` ` `// Driver Code``int` `main()``{``    ``// Function that prints``    ``// the value of pi``    ``printValueOfPi();``    ``return` `0;``}`
Output:
```3.141593
```

Method 3: Using inbuilt constant value define in the “cmath” library:
The value of Pi(π) can directly written using the constant stored in cmath library. The name of the constant is M_PI. Below is the program for printing the value of Pi:

 `// C++ program for the above approach``#include "cmath"``#include "iostream"``using` `namespace` `std;`` ` `// Function that prints the``// value of pi``void` `printValueOfPi()``{``    ``// Print value of pi``    ``printf``(``"%f\n"``, M_PI);``}`` ` `// Driver Code``int` `main()``{``    ``// Function that prints``    ``// the value of pi``    ``printValueOfPi();``    ``return` `0;``}`
Output:
```3.141593
```
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