# trig

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sin^4 x = (3-4cos 2x + cos4x)/8

• trig -

just simplify both sides! easy as that!!!

• trig -

how?

• trig -

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

• trig -

1-4cos2x+cos4x/8=sin4x

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