Method #1 – Area from the Radius
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Formula – How to calculate the area of a semicircle from the radius
π is approximately equal to 3.1415926535
Area = (π x Radius2) ÷ 2
Example
A semicricle has a radius of 10 inches.
Area = (π x 102) ÷ 2
Area = (3.14159 x 100) ÷ 2
Area = 314.159 ÷ 2
Area = 157.0795 inches2
Method #2 – Area from the Diameter
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Formula – How to calculate the area of a semicircle from the diameter
π is approximately equal to 3.1415926535
Step 1: Find the Radius from the Diameter
Radius = Diameter ÷ 2
Step 2: Find the Area from the Radius
Area = (π x Radius2) ÷ 2
Example
A semicircle has a diameter of 20
Radius = 20 ÷ 2 = 10
Area = (π x 102) ÷ 2
Area = (3.14159 x 100) ÷ 2
Area = 314.159 ÷ 2
Area = 157.0795 inches2
Method #3 – Area from the Circumference
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Formula – How to calculate the area of a semicircle from the circumference
π is approximately equal to 3.1415926535
Step 1: Calculate the radius from the circumference
Radius = Circumference ÷ π
Step 2: Calculate the area from the radius
Area = (π x Radius2) ÷ 2
Example
A semicircle has a circumference of 10
Radius = 10 ÷ π = 10 ÷ 3.14159 = 3.183102
Area = (π x 3.1831022) ÷ 2
Area = (3.14159 x 10.13214) ÷ 2
Area = 31.83103 ÷ 2
Area = 15.9155