SOLUTION: Find the exact value given that sin A = -4/5 with A in quadrant IV, tan B= 7/24 with B in quadrant III, and cos C= -5/13 with C in quadrant II Cos 2A

Question 766927: Find the exact value given that sin A = -4/5 with A in quadrant IV, tan B= 7/24 with B in quadrant III, and cos C= -5/13 with C in quadrant II
Cos 2A
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
Find the exact value given that sin A = -4/5 with A in quadrant IV
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Since sin = y/4, y = -4 and r = 5
Then x = sqrt[5^2-4^2] = sqrt[9] = 3
So cos(A) = 3/5
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Cos 2A = cos^2(A)-sin^2(A) = (3/5)^2 - (4/5)^2 = -7/25
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Cheers,
Stan H.
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