posted by ALISON on .
An automobile windshield washer 10inches long rotates an angle of 60degrres. If the rubber part of the blade only covers the last 9inches of the wiped, find the area of the windshield cleaned by the wiper.
The wiper covers 60 deg, or 1/6 of a circle. The area of a circle is πr^2. So, the area of a 10" circle is 100π. But we have to subtract the area of a 1" circle, since the rubber does not cover the inside inch. That would be π. So, a whole 10" circle minus a 1" circle would be 99π. But we only have 1/6 of that, or 16.5π = 51.8 sq. in.