SOLUTION: cos(a) - 2sin^2 (a)-1 = 0

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Question 441147: cos(a) - 2sin^2 (a)-1 = 0
Answer by lwsshak3(11628) About Me  (Show Source):
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cos(a) - 2sin^2 (a)-1 = 0
..
cos(a) - 2sin^2 (a)-1 = 0
cosa-2(1-cos^2a)-1=0
cosa-2+2cos^2a-1=0
cosa+2cos^2a-3=0
2cos^2a+cosa-3=0
(2cosa+3)(cosa-1)=0
2cosa+3=0
cosa=-3/2 (reject, not in domain)
cosa-1=0
cosa=1
a=0 degrees (a<360)