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mikeph
mikeph is online now
#2
Nov19-12, 10:16 AM
P: 1,197
It's really hard to answer these questions when you don't specify what any of the terms mean, so I can only guess at what r-r' even is. It looks like a Pythagoras approach to give you the hypotenuse of the triangle with sides r and z-z0.

How would you use the law of cosine, and what problem would using it solve?