Prove that cos^-1(1/5)+cos^-1(5/7)+cos^-1(19/35) = Pie without the use of a calculator? How would I do this?
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Originally Posted by zweevu Prove that cos^-1(1/5)+cos^-1(5/7)+cos^-1(19/35) = Pie without the use of a calculator? How would I do this? Several approaches are possible. One approach might be the following: Let , and . Now evaluate by applying the compound angle formula several times. Note: Find , and by using the known values for cos and applying the Pythagorean Identity.
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