Exact Area = 25pi square units
Approximate Area = 78.5 square units
The approximate value is found using pi = 3.14
====================================================
Step-by-step explanation:
I think you meant to say "quarter circle" instead of "semicircle".
The area of a full circle with radius r = 10 is
A = pi*r^2
A = pi*10^2
A = pi*100
A = 100pi
But we only want one quarter of this. So we divide the full area by 4
(100pi)/4 = (100/4)pi = 25pi
The exact area in terms of pi is 25pi square units
If we used the approximation pi = 3.14, then we can say 25*pi = 25*3.14 = 78.5 is the approximate area
To get a better approximation, use more decimal digits in pi.