Question 138472
cos^2 2x - sin^2 2x=0 

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cos^2(2x) - [ 1-cos^2(2x)] = 0
2cos^2(2x) = 1
cos^2(2x) = 1/2
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cos(2x) = sqrt(2)/2
2x = 45 degrees or -45 degrees
x = 22.5 degrees or -22.5 degrees

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Cheers,
Stan H.