Answer :

AL2006

The area of a whole circle is (pi) (radius²) .

So the area of half of it would be  (1/2) (pi) (radius²) .

If you don't know the radius, then you can use the formula     

                           Area = (1/8) (pi) (diameter²) .


You just find the area of a circle then divide it by 2
Area = Radius × Radius × [tex] \frac{22}{7} [/tex] (or pi)
Then divide your area by 2 and you get the semi-circle's area.