# What are non differentiable points for a graph?

##### 1 Answer

Jul 24, 2014

Since a function that is differentiable at **discontinuities** .

On the other hand, if the function is continuous but not differentiable at

1) the **tangent line is vertical** (and that does not have a slope)

2) the difference quotient **different one-sided limits** at

See this video on differentiability for details and pictures.