How to Calculate Area of a Semicircle

A semicircle is half of a circle. So to calculate the area of a semicircle, you just need to calculate the area of the circle and then divide it by two. If you want to calculate the area of the semicircle faster, see Step 1 to get started.

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Steps

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Find the radius of the semicircle. You will need the radius to find the area of the semicircle. Assume the radius of the semicircle is 5 cm.

If given the diameter of the circle, you must divide it by two to get the radius. For example, if the diameter of the circle is 10 cm, then you divide 10 by 2 (10/2) to get 5 cm as the length of the radius.

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Calculate the area of the circle and divide it by two. The formula for calculating the area of a circle is πr ² , where “r” is the radius of the circle. Since you’re looking for the area of a semicircle, you need to calculate half the area of the circle, which means using the formula for the area of the semicircle and then dividing it by two. So the formula used to find the area of a semicircle is πr ² /2 . Now, put the value “5 cm” into the formula to get the result. You can use the rounded value of π to calculate, which is 3.14, or just keep the symbol in the formula. Here is the calculation:

Area = (πr ² )/2
Area = (π x 5 cm x 5 cm)/2
Area = (π x 25 cm ² )/2
Area = (3.14 x 25 cm ² )/2
Area = 39.25 cm ²

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Remember to give results in square units. Since this is the unit used to calculate the area of a figure, square units (eg cm ² ) must be used in your answer to show that you are calculating a two-dimensional object. If you are calculating volume, use cubic units (eg cm ³ ).

Advice

The area of the semicircle is (1/2)(pi)(r^2).
The area of the circle is (pi)(r^2)

Warning

Note do not use the attached line to calculate the area! If given a diameter, then you must remember to divide by 2 to get the length of the radius.

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Advice

Warning

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