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Copy of Law of Cosines

In class we were talking about relating the Law of Cosines to the Pythagorean Theorem. Most of the proofs I know for the one come from the other. So here's a look at the LoC from the viewpoint of Euclid's slick proof of the Pythagorean Theorem, and using the favorite Greek geometry trick, dropping an altitude. Irina Boyadzhiev has a sweet animation of the proof from this viewpoint.
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