# 1. Introduction

A circle is one of the fundamental shapes in geometry. The area of a circle is given by the formula: ( A = pi r^2 \), where r stands for the radius of the circle.

Computing the area of a circle is a foundational concept in math and has various applications in science and engineering. This article will guide you on how to design an R program that calculates the area of a circle given its radius.

# 2. Program Overview

The program will prompt the user to input the radius of the circle. It will then compute the area using the formula mentioned and display the result to the user.

# 3. Code Program

``````# Define the value of Pi
pi <- 3.141592653589793

# Prompt the user to enter the radius of the circle
cat("Enter the radius of the circle: ")

# Calculate the area of the circle

# Display the computed area to the user
``````

### Output:

```Enter the radius of the circle: 5
The area of the circle with radius 5 is: 78.5398163397448
```

# 4. Step By Step Explanation

1. Our program commences by defining the value of pi. Though there are various ways to determine the value of pi in R, for simplicity, we've defined it as a constant with its generally accepted value.

2. The user is prompted to provide the radius of the circle using the cat function.

3. The readLines(n=1) function is employed to capture the user's input, which is then converted into a numeric value using as.numeric and stored in the radius variable.

4. Following the acquisition of the radius, the program computes the area of the circle using the formula ( A = pi r^2 \). This calculated value is saved in the area variable.

5. Finally, the program leverages the cat function to present the calculated area of the circle to the user.