1) The derivative rule for inverses states that if a function f is differentiable on an interval and its derivative f' is never zero on that interval, then the inverse function f^-1 is also differentiable on that interval. The derivative of the inverse is equal to the reciprocal of the derivative of the original function. 2) As an example, the inverse of the natural logarithm function ln(x) is the exponential function e^x. 3) By applying the inverse derivative rule, we can show that the derivative of the exponential function e^x is itself, or de^x/dx = e^x.