I’m going to change to decimals just because it’s easier for me but I’ll change it back.
The formula for area of a circle is pi times radius squared.
Pi is 3.14
Radius is 1.25 (3.5 divided by 2)
And square the radius which is 1.25 times 1.25 which is 6.25
Next multiply 6.25 by 3.14
The area of a full circle would be 19.625, however the window is a semicircle. So divide 19.625 by 2 which is 9.8125 and add a feet squared afterwards.
To convert back to fractions, round the decimal to the nearest hundredth, 9.81 and put it over 100
(9 81/100 ft squared is your full answer)