Question

sin3x*cosx*cosx*cosx+cos3x*sinx*sinx*sinx

Answer 1

If its cube...use the identity of acube + bcube...it may help

Answer 2

cos(x) appears thrice, and so does sin(x).
so=

$sin(3x)cos(x)cos(x)cos(x)+cos(3x)sin(x)sin(x)sin(x) \\ sin(3x)(cos(x))^3+cos(3x)+(sin(x))^3 \\ (sin3x+cos3x)(cosx+sinx)^3$

Ans= $(sin3x+cos3x)(cosx+sinx)^3$