automobiles suppose the arm of a windshield wiper is 16 in. long, with a blade 12 in. long. if the wiper moves through an angle of 90degree, how much of the windshield is cleaned in one pass of the wiper ?

Answer 1

sketch a quarter circle with an outer radius of 16
and an inner radius of 4
So the area not wiped has to be subtracted form the area of the whole quarter circle, so ...

find the area of 1/4 circle with radius 16
find the area of 1/4 circle with radius 4
subtract and you are done.