## Area of a Semicircle Lesson

### Semicircle Area Formula

The formula for area of a semicircle is given as:

**A = ^{1}⁄_{2}πr^{2}**

Where *A* is the area and *r* is the radius.

INTRODUCING

### Area of a Semicircle Example Problems

Let's go through a couple of example problems together to practice finding the area of a semicircle.

#### Example Problem 1

What is the area of a semicircle with a radius of 5?

Solution:

- Let's plug the radius into the area formula.
- A =
^{1}⁄_{2}πr^{2} - A =
^{1}⁄_{2}π(5^{2}) = 12.5π **The area is 12.5π.**

#### Example Problem 2

A semicircle's area is measured to be 4.5π square meters. What is the radius in meters?

Solution:

- Let's plug the area into the formula.
- A =
^{1}⁄_{2}πr^{2} - 4.5π =
^{1}⁄_{2}πr^{2} - Now we will solve for the radius
*r*. - 4.5 =
^{1}⁄_{2}r^{2} - r
^{2}= 9 - r = 3
**The radius is 3 meters.**