Posted by Rachel on Monday, February 23, 2009 at 8:15pm.
sin^4 x = (34cos 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
how?

trig  Reiny, Monday, February 23, 2009 at 9:21pm
RS
= (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
= (2(2sin^2(x))^2)/8
= (8sin^4(x))/8
= sin^4(x)
= LS
hope I made no typos this time
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