$\displaystyle \begin{array}{{>{\displaystyle}l}} y=cos^{6} x+2sin^{4} xcos^{2} x+3sin^{2} xcos^{4} x+sin^{4} x\\ y'=-6cos^{5} xsinx+8sin^{3} xcos^{3} x-4sin^{5} xcosx\\ \ \ \ \ \ \ \ \ +6sinxcos^{5} x-12sin^{3} xcos^{3} x+4sin^{3} xcosx\\ =-4sin^{5} xcosx-14sin^{3} xcos^{3} x+4sin^{3} xcosx \end{array}$