Semicircle with radius 5.0000 cm: area is 39.2699 cm².
The area is 39.2699 cm², which is exactly half the area of a full circle with the same radius.
The arc length (15.7080 cm) is half the full circle circumference. The perimeter (25.7080 cm) adds the straight diameter edge (10.0000 cm) on top.
A common mistake is treating the perimeter as just the arc. The full boundary also includes the straight diameter edge, making the perimeter equal to r × (π + 2) ≈ 25.7080 cm.
Next stepTo scale this semicircle up, multiply the radius by your scale factor and the area will scale by its square.