What is the slope of the tangent line at a minimum of a smooth curve?

1 Answer
Aug 3, 2014

The slope is 00.

Minima (the plural of 'minimum') of smooth curves occur at turning points, which by definition are also stationary points. These are called stationary because at these points, the gradient function is equal to 00 (so the function isn't "moving", i.e. it's stationary). If the gradient function is equal to 00, then the slope of the tangent line at that point is also equal to 00.

An easy example to picture is y=x^2y=x2. It has a minimum at the origin, and it is also tangent to the xx-axis at that point (which is horizontal, i.e. a slope of 00). This is because dy/dx=2xdydx=2x in this case, and when x=0x=0, dy/dx=0dydx=0.

![Graph of a curve showing a mathematical formula with a http://tangent.](https://useruploads.socratic.org/icdMFD1zSg20xaAcyihb_tangentline.PNG)