1. The problem statement, all variables and given/known data This is a problem within a problem. I need to differentiate the area of a chord of find the maximum area (and hopefully, in the process, radius). 2. Relevant equations I found this equation on another site: A=R^2[(Pi/180*c - sin c)]/2 Where: • C is the central angle in degrees. • R is the radius of the circle of which the segment is a part. • A is the area of the chord. (I think I typed it out correctly. Here's the website: http://www.mathopenref.com/segmentarea.html) 3. The attempt at a solution First problem: How can I differentiate the equation when the is denominator is 2? My central angle is 180 Degrees, so it worked out to be: A=R^2[(Pi - sin 180)]/2 Something is terribly wrong, I'm sure. Is it even the right formula? There is also this formula: http://mathworld.wolfram.com/Chord.html Sorry it's a little messy, but my thought pattern is crazy at the moment. Thanks for any help.