A semi circle is half of a circle, so we will divide it by 2 after finding the area.
Formula for finding semi circle = pi x radius ÷ 2
Formula for radius = diameter ÷ 2
Radius = 36 ÷ 2 = 18mm
Semi circle = 3.14 or 22/7 x 18 = 56.57
56.57 ÷ 2 = 28.285
Note: I don't have a calculator with me right now, so you might want to consider typing out pi x 18 ÷ 2 on a calculator since my answer might be wrong because the answer has endless decimals.
