How do you find the area and perimeter of a half circle?

Find the area and perimeter of the full circle, then throw away 1/2 of each.

Perimeter (circumference) of a circle = (pi) times (diameter).

For a half circle, it's (1/2 pi) times (diameter)

Area of a circle = (pi) times (radius)2

For a half circle, it's (1/2 pi) times (radius)2