Concept question--exponential function derivatives (calc II) Ok, so there is an example on my textbook that asks for the derivative of y = x^2. --after applying ln on both sides, if finally gets to the lny = xlnx step. But after this step, it just states y'/y = x(1/x)+ lnx(1). I understand it is just the prod. rule on the right, but can anyone explain why it went from lny to y'/y ? Is this a property or formula that they used? Thank you.