AP Test Review Help - Area of Region

**Let R be the region in the first quadrant enclosed by the graph of y=2cosx, the x-axis, and the y-axis.**

A) Find the area of the region R.

B) If the line x=a divides the region R into two regions of equal area, find a.

C) Find the volume of the solid obtained by revolving region R about the x-axis.

D) If R is the base of a solid whose cross sections perpendicular to the x-axis are semi-circles, find the volume of the solid.

I've been having trouble with problems like these... I can never figure out how to find the area and volume of these figures with so many lines.