# Pi(π) in C++ with Examples

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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