Note: color(white)("XXX")(d (arctan(x)))/(dx)=1/(1+x^2)
and color(white)("XXX")(d(x^3))/(dx)=3x^2
Using the chain rule: color(white)("XXX")(d(color(blue)((color(red)(arctan(x)))^3)))/(d(color(green)x))=(d(color(blue)((color(red)(arctan(x)))^3)))/(d(color(red)(arctan(x)))) * (d(color(red)(arctan(color(green)x))))/(dcolor(green)x)