# C Program to Find Area of Circle

The area of a circle is the region enclosed by the circle’s boundary. In this article, we will learn the program to find the area of a circle in C programming.

The area of a circle can simply be evaluated using the formula:

`Area = Pi * r2`

where r is the radius of the circle and the value of Pi is 3.14159265358.

### Algorithm to Find Area of Circle in C

• Define a constant PI with the value of 3.142.
• Create a function findArea.
• Within the findArea function, Multiply PI by the square of the radius r and return the result.

## C

 `// C program to find the area of ``// the circle using radius ``#include ``#include ``#define PI 3.142 `` ` `// Function to find the area of ``// of the circle ``double` `findArea(``int` `r) { ``return` `PI * r * r; } `` ` `// Driver code ``int` `main() ``{ ``    ``printf``(``"Area is %f"``, findArea(5)); ``    ``return` `0; ``}`

Output
`Area is 78.550000`

### Complexity Analysis

Time Complexity: O(1)

Auxiliary Space: O(1)

Please refer complete article on Program to find the area of a circle for more details.

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