Posted by Rachel on Monday, February 23, 2009 at 8:15pm.
sin^4 x = (3-4cos 2x + cos4x)/8
prove on one side please!
trig - myschic, Monday, February 23, 2009 at 8:21pm
just simplify both sides! easy as that!!!
trig - Rachel, Monday, February 23, 2009 at 8:33pm
trig - Reiny, Monday, February 23, 2009 at 9:21pm
= (3 - 4cos(2x) + cos^2(2x) - sin^2(2x))/8
= (3 - 4cos(2x) + cos^2(2x) - (1 - cos^2(2x)))/8
= (2cos^2(2x) - 4cos(2x) + 2)/8
= (2(cos^2(2x) - 2cos(2x) + 1))/8
= (2(cos(2x) - 1)^2)/8
= (2(1 - 2sin^2(x) - 1)^2)/8
hope I made no typos this time
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