# 1. Introduction

The area of a circle is a fundamental concept in geometry, often used in various applications, from design to engineering calculations. The formula to find the area of a circle is given by: A = πr^2, where "A" is the area, and "r" is the radius of the circle. In this guide, we'll create a Swift program to calculate the area of a circle given its radius.

# 2. Program Overview

Our program will accept the radius of a circle as an input and then compute its area using the formula mentioned above.

We'll make use of Swift's built-in constants and mathematical functions to accomplish this.

# 3. Code Program

``````// Declare the radius of the circle
let radius: Double = 5.0

// Calculate the area using the formula
let area = Double.pi * radius * radius

// Display the calculated area
print("Area of the circle with radius \(radius) is \(area)")
``````

### Output:

```Area of the circle with radius 5.0 is 78.53981633974483
```

# 4. Step By Step Explanation

1. let radius: Double = 5.0: We define a constant radius of type Double and assign it the value of 5.0. This represents the radius of our circle.

2. let area = Double.pi * radius * radius: Here, we calculate the area of the circle. Double.pi is a built-in constant in Swift that provides the value of π (pi) to several decimal places. We then multiply π with the square of the radius to get the area.

3. The print statement, print("Area of the circle with radius \(radius) is \(area)"), displays the radius of the circle and its corresponding area. Swift's string interpolation allows us to embed the values of the radius and area constants directly into the string for display.