Mathematics

Mathematics

Problem

The variables xx and yy are related by yln⁡y=xy \ln y = x with y>0y>0. Determine dydx\dfrac{dy}{dx} and hence find its value at the point where y=ey=e.
Intuitive explanation

This problem asks you to find a derivative when yy is defined implicitly through a transcendental equation rather than as an explicit function of xx. The key insight is to differentiate both sides of the equation yln⁡y=xy \ln y = x with respect to xx using the product rule on the left side, treating yy as a function of xx. Once you have dydx\frac{dy}{dx} in terms of yy, substituting y=ey = e gives you the specific slope at that point.

Intuitive explanation

This problem asks you to find a derivative when yy is defined implicitly through a transcendental equation rather than as an explicit function of xx. The key insight is to differentiate both sides of the equation yln⁡y=xy \ln y = x with respect to xx using the product rule on the left side, treating yy as a function of xx. Once you have dydx\frac{dy}{dx} in terms of yy, substituting y=ey = e gives you the specific slope at that point.

Browse the problem library