# How to get the value of Pi in C++

In this article, you will learn about how to get the value of Pi in C++ with several methods. A few of the mathematical functions in C++ are used to determine Pi(π).

### 1. Making Use of Pre-Defined Constants

The M_PI constant is available in C and C++ and is frequently found in the <cmath> or <math.h> header. It stands for the number Pi. It can be used directly for Pi-based mathematical computations in your C++ program.

Example:

Let's take an example to get the value of pi using pre-defined constants in C++:

Output:

```The value of Pi is: 3.14159
```

Explanation:

1. The header files required for input/output operations (<iostream>) and mathematical functions (<cmath>) are included using the #include directives.
2. The program's entrance point serves as its main function.
3. double pi = M_PI; line initializes a double variable pi to the value of the predefined constant M_PI, which stands for the mathematical constant Pi. Usually, the <cmath> or <math.h> header file contains this constant.
4. The words "The value of Pi is: " and the value of pi is printed to the standard output stream using the std::cout statement. After printing the message, a new line is added using the std::endl function.
5. return 0; signifies the end of the main function and the successful execution of the program.

### 2. Making Use of Mathematical Functions

A numeric number between [-] and [+] is returned by the acos() function, which is used to calculate the value of pi.

Acos(0.0) will produce the value for /2 when used.

An approximation of Pi can also be obtained by using different mathematical functions, such as acos(-1) or atan(1) * 4. T hese equations use trigonometric or inverse trigonometric functions to determine the value of Pi.

Example:

Let's take an example to get the value of pi using mathematical functions in C++:

Output:

```An approximation of Pi is: 3.14159
```

Explanation:

1. The header files required for input/output operations (<iostream>) and mathematical functions (<cmath>) are included using the #include directives.
2. The main function serves as the program's execution's beginning point.
3. double pi_approx = atan(1) * 4; line uses the atan() function to compute an approximation of Pi. The arctangent of 1, which is equal to /4 in radians, is calculated using the phrase atan(1). An approximate value of π can be obtained by multiplying this value by 4.
4. The text "An approximation of Pi is: " and pi_approx's value is printed to the standard output stream using the std::cout command. After printing the message, a new line is added using the std::endl function.
5. return 0; signifies the end of the main function and the successful execution of the program.

### 3. Utilizing the asin() function

The asin() function is used to calculate the value of Π and returns a numeric value between [-Π, Π]. Given that asin(1.0) will get the result for Π/2. Consequently, to find the value of Π:

The value derived from the equation above is now calculated as follows:

Example:

Let's take an example to get the value of pi using asin function in C++:

Output:

```The value of pi is: 3.141593
```

Explanation:

1. #include directive in competitive programming environments, the most standard libraries can be included by using the shorthand "bits/stdc++.h". It contains every header file from the standard library.
2. Program items can be used from the standard namespace without being explicitly specified due to the using namespace std; declaration.
3. It is possible to compute and print the value of Pi using the print_ValueOfPi function, which is defined.
4. The formula to find Pi is double pi = 2 * asin(1.0). When the arc sine of an argument is calculated using the asin() function, it returns π/2, which may be multiplied by two to find Pi.
5. The program's execution entry point is known as the main function.
6. The main function calls the print_ValueOfPi function to print the value of Pi.
7. return 0; signifies the successful execution of the program and the end of the main function