3/23/15

A block of wood has the shape of a right circular cylinder with radius  and height , and its entire surface has been painted blue. Points A and B are chosen on the edge of one of the circular faces of the cylinder so that arc AB on that face measures 120 degrees. The block is then sliced in half along the plane that passes through point A, point B, and the center of the cylinder, revealing a flat, unpainted face on each half. The area of one of these unpainted faces is a*pi + b*sqrt(c), where a, b, and c are integers and c is not divisible by the square of any prime. Find a+b+c.

Hint: Use angle relations and right triangles.

Level: 7