#24 · Circles · Classes 6–12
Semicircle
Half of a circle cut along a diameter.
Semicircle📐 Formula
Area = ½πr²; Perimeter = πr + 2r
✏️ Worked example
r = 4: area = 8π ≈ 25.13, perimeter ≈ 20.57.
🌍 Where it is used
Protractors, arched windows and tunnels.
❓ Quick check
Area of a semicircle with r = 2: