y' = (6x^3)' sinx + 6x^3 (sinx)' = 18x^2 sinx + 6x^3 cosx
y' = (4x^3)' sinx + 4x^3 (sinx)' = 12x^2 sinx + 4x^3 cosx
y' = (6x^3)' sinx + 6x^3 (sinx)' = 18x^2 sinx + 6x^3 cosx
y' = (4x^3)' sinx + 4x^3 (sinx)' = 12x^2 sinx + 4x^3 cosx