Show that d dx d d dx Inkx Compute the derivative of the natural log of kx Begin by letting u kx and substituting u into the equation d In kx In u dx Compute the derivative using the chain rule In u dx d 1 d u dx In x given that x 0 and k 0 is a real number dx u Substitute kx back in for u where it appears in the equation RILE x In kx x kx