Question 1177495
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sin(2x) = 2sin(x)*cos(x).


THEREFORE,  sin^4(2x) = (2sin(x)*cos(x))^4 = 16cos^4(x)*(1-cos^2(x))^2 = 16cos^4(x)*(1-2cos^2(x) + cos^4(x)).


It is the formula you are looking for.



If necessary, you can apply FOIL to the last expression.
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