1. The problem statement, all variables and given/known data Figure 8-29 shows a thin rod, of length L and negligible mass,that can pivot about one end to rotate in a vertical circle. A heavyball of mass m is attached to the other end. The rod is pulled asidethrough an angle 6 and released.As the ball descends to its lowestpoint, (a) how much work doesthe gravitational force do on itand (b) what is the change in thegravitational potential energy ofthe ball-Earth system? (c) If thegravitational potential energy istaken to be zero at the lowestpoint, what is its value just as theball is released? (d) Do the mag-nitudes of the answers to (a)through (c) increase, decrease, orremain the same if angle 6 is in-creased? 2. Relevant equations http://www.niu.edu/~debrown/Spring2009/Q4_5.09.pdf [Broken] if you click this link, scroll down to problem two for the image. 3. The attempt at a solution i know how to do the problem, the only thing i cannot figure out is how to find the height. I googled the problem and someone said that the change in y should be L-Lcos(theta)....and when i used that it worked, but i don't know why. It's problably some simple geometry thing but I need to know what L-Lcos(theta) means in case i get a problem similar to this on an exam.