SOLUTION: Can’t we use the formula cox2x=2cos^2x-1 or 1-2sin^2x while solving cos2x=0

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Question 1116246: Can’t we use the formula cox2x=2cos^2x-1 or 1-2sin^2x while solving cos2x=0
Answer by KMST(5328) About Me  (Show Source):
You can put this solution on YOUR website!
You could,
but it seems more direct to think of
cos%282x%29=0 --> 2x=pi%2F2%2Bk%2Api for any k integer,
and from there solve for x as
x=pi%2F4%2Bk%2Api%2F2 for any k integer.

One of your alternatives is
cos%282x%29=0 --> 2cos%5E2%28x%29-1=0 --> cos%5E2%28x%29=1%2F2 --> cos%28x%29=%22+%22+%2B-+sqrt%282%29%2F2 --> x=pi%2F4%2Bk%2Api%2F2 for any k integer.