Question
If cos2B = sin(1.5B - 36 o ) , then find the measure of 'B'.
Solution
We know that, cosA = sin(90 o  - A)
cos2B = sin(1.5B - 36 o )
Or, sin(90 o  - 2B) = sin(1.5B - 36 o )
Or, 90 o  - 2B = 1.5B - 36 o
Or, 2B + 1.5B = 90 o  + 36 o
So, B = (126 o /3.5) = 36 o
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