**The Program in C to Find out the Area by PIE is given below**:

```
#include <stdio.h>
#include <math.h> // for M_PI constant
int main() {
double radius, area;
printf("Enter the radius of the circle: ");
scanf("%lf", &radius);
area = M_PI * pow(radius, 2); // pi * r^2
printf("The area of the circle with radius %lf is %lf", radius, area);
return 0;
}
```

## Output:

Enter the radius of the circle: 7

The area of the circle with radius 7.000000 is 153.860000

## Pro-Tips**💡**

This program uses the `scanf`

function to read a double value input by the user and store it in the variable `radius`

.

The `pow`

function from math.h library is used to calculate the square of the radius, and then the area of the circle is calculated using the formula pi * r^2.

The `printf`

function is then used to print the area of the circle.

Note that the PI is defined as a constant using `#define`

preprocessor statement, which assigns a value of 3.14 to the constant PI, which can be used in the area calculation.

Please keep in mind that this is an approximation of PI and the value of PI is defined up to 15 decimal places.

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