Question 694809: cos[ sin^-1 (-5/13)- cos^-1 (12/13]
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! cos[ sin^-1 (-5/13)- cos^-1 (12/13]
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Assume A is in QIII
Let A = sin^-1(-5/13), then cos(A) = -12/13
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Assume B is in QI
Let B = cos^-1)(12/13), then sin(B) = 5/13
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Your Problem:
cos[A + B] = cos(A)(cos(B))- sin(A)(sin(B)
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= (-12/13)(12/13) - (-5/13)(5/13)
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= (-144 + 25)/13^2
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= -0.7041
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Cheers,
Stan H.
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