sin^3(4x)的导数怎么算?

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sin^3(4x)的导数怎么算?

令u=4x,则sin^3(4x)=sin^3(u);
d[sin^3(4x)]/dx={d[sin^3(4x)]/du}{du/dx}={d[sin^3(u)]/du}{du/dx}
=3sin^2(u)·cos(u)·{d(4x)/dx}
=4·3sin^2(u)·cos(u)
=12sin^2(4x)·cos4x)

(sin平方4x)'sin4x+4cos4xsin平方4x=(4cos4xsin4x*2)sin4x+4cos4xsin平方4x=6sin4xsin8x