Posted by CHEYANNE on Monday, February 27, 2012 at 2:54am.
cos(4x) = 2cos^2(2x)-1
cos2x = 2cos^2(x) - 1
cos(4x) = 2(2cos^2(x)-1)^2 - 1
= 2(4cos^4(x) - 4cos^2(x)+1) - 1
= 8cos^4(x) - 8cos^2(x) + 1
or,
sin^4(x) + cos^4(x) -6 sin^2(x)cos^2(x)
or a bunch of other expressions
cos(x/2) = sqrt[(1 + cos(x))/2
sin(x/4) = sqrt[(1 - cos(x/2))/2)
= sqrt([1-(sqrt[(1+cos(x))/2)]/2)
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