SOLUTION: Find cos(A+B) given angle A is in quadrant 1, angle B is in quadrant 2, and sinA=5/13 and cosB= -3/5

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Question 934488: Find cos(A+B) given angle A is in quadrant 1, angle B is in quadrant 2, and sinA=5/13 and cosB= -3/5
Answer by lwsshak3(11628) About Me  (Show Source):
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Find cos(A+B) given angle A is in quadrant 1, angle B is in quadrant 2, and sinA=5/13 and cosB= -3/5
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sinA=5/13
cosA=12/13
..
cosB=-3/5
sinB=4/5
..
cos(A+B)=cosAcosB-sinAsinB=12/13*(-3/5)-5/13*4/5=-36/65-20/65=-56/65