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Given sina= 3/4 and cosB = (-5)/13 and this is Quad II find cos(a+B)Asked by joel
Given sina= 3/4 and cosB = (-5)/13 and this is Quad II find cos(a+B)
Answers
Answered by
drwls
Use the formula
cos (A + B) = cos A cos B - sin A sin B
It will help to know that
sin B = 12/13 (if B is in the 2nd quadrant), and
cos A = -(sqrt7)/4 (if A is in the second quadrant)
Those values can be obtained with
sin^2 + cos^2 = 1
You don't say which angle in in the second quadrant. Is it A, B or A+B?
cos (A + B) = cos A cos B - sin A sin B
It will help to know that
sin B = 12/13 (if B is in the 2nd quadrant), and
cos A = -(sqrt7)/4 (if A is in the second quadrant)
Those values can be obtained with
sin^2 + cos^2 = 1
You don't say which angle in in the second quadrant. Is it A, B or A+B?
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