A semicircle is a one-dimensional locus of points that forms half of a circle. The area is simply half of the full circle's area. However, the perimeter is not just half—it includes the curved arc plus the straight diameter.
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Pro Tips
The perimeter is πr + 2r.
A semicircle's central angle is always 180°.
The angle subtended by a semicircle at any point on the arc is always a right angle (90°).
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Fun Facts
"Semicircles are widely used in architecture, particularly in Roman arches."
"A protractor is a common tool shaped like a semicircle."
"The 'upper half plane' in complex analysis is essentially an infinite semicircle."
