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Unformatted text preview: B acute and obtuse. By similar arguments for A and C we get the other two formulas. QED Note that we did not prove the Law of Cosines for right triangles, since it turns out (see Exercise 15) that all three formulas reduce to the Pythagorean Theorem for that case. The Law of Cosines can be viewed as a generalization of the Pythagorean Theorem. Also, notice that it sufces to remember just one of the three formulas (2.9)(2.11), since the other two can be obtained by cycling through the letters a , b , and c . That is, replace a by b , replace b by c , and replace c by a (likewise for the capital letters). One cycle will give you the second formula, and another cycle will give you the third....
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This note was uploaded on 01/21/2012 for the course MAC 1130 taught by Professor Dr.cheun during the Fall '11 term at FSU.
 Fall '11
 Dr.Cheun
 Calculus, Pythagorean Theorem, Law Of Cosines

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