# 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:

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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 pivoid printValueOfPi(){      // Find value of pi using    // acos() function    double pi = 2 * acos(0.0);      // Print value of pi    printf("%f\n", pi);}  // Driver Codeint 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 pivoid printValueOfPi(){      // Find value of pi using    // asin() function    double pi = 2 * asin(1.0);      // Print value of pi    printf("%f\n", pi);}  // Driver Codeint 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 pivoid printValueOfPi(){    // Print value of pi    printf("%f\n", M_PI);}  // Driver Codeint main(){    // Function that prints    // the value of pi    printValueOfPi();    return 0;}
Output:
3.141593

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