## What Is a Semicircle?

A semicircle is a two-dimensional geometric shape that is formed by dividing a circle into two equal parts, where one part is a half-circle. The boundary of a semicircle consists of an arc and a diameter that connects the endpoints of the arc. The diameter of a semicircle is twice the length of its radius.

The word “semi” means half, so a semicircle is literally half of a circle. It has rotational symmetry of 180 degrees, which means that it looks the same when rotated by 180 degrees around its center.

## Area of a Semicircle

The area of a semicircle is half of the area of the corresponding full circle.

If r is the radius of the semicircle, then

Area of circle = πr²,

where π (pi) is a mathematical constant approximately equal to 3.14159.

So, the area of the semicircle is:

½ * πr²

or

Area of semicircle = πr² / 2

Therefore, the area of a semicircle is equal to half the area of a circle.

### How to Find the Area of a Semicircle

To find the area of a semicircle, you can use the following formula:

Area of a semicircle = (π * r²)/2

Where r is the radius of the semicircle, and π (pi) is a mathematical constant approximately equal to 3.14159.

Steps to find the area of a semicircle:

**Step1.** Measure the radius of the semicircle. The radius is the distance from the center of the circle to the edge of the semicircle.

**Step 2.** Square the radius. Multiply the radius by itself.

**Step 3.** Multiply the squared radius by pi. Use the value of pi as 3.14159.

**Step 4.** Divide the result by 2 to get the area of the semicircle.

**For example,** let’s say the radius of the semicircle is 5 cm. To find the area of the semicircle, we can use the formula:

Area of a semicircle = (π * r²)/2

= (3.14159 * 5²)/2

= (3.14159 * 25)/2

= 39.27 cm²

Therefore, the area of the semicircle is 39.27 square centimeters.

### Area of Semicircle Formula

The formula for the area of a semicircle is:

where:

A = area of the semicircle

r = radius of the semicircle

π ≈ 3.14159 (pi, a mathematical constant representing the ratio of the circumference of a circle to its diameter)