Example CCD.DDS.R:Functions that use the roots (square, cube. or others) in the
definition are commonly used to illustrate functions that are not differentiable
at a single point (a singularity for the function).

Consider $f(x) = 2 \sqrt [3]{x-1} - 1$ at $x=1$ in the GeoGebra sketch below with
both mapping diagram and graph to visualize the failure of the limit in
the definition of the derivative.

Martin Flashman, Sept. 9, 2016,
Created with GeoGebra

Notice how the points on the graph are paired with the points
on the mapping diagram.

Check the box** Show Second Pair** to see the second pair of data used to estimate a possible numerical value for the derivative of $f$.

You can change the values of $h$ with the slider.

Check the box** Show Derivative...** to see tangent line and focus point for all numbers $x_0 \ne 1$ by moving x_0 on the source axis.

You can explore similar examples by changing the functions in the input box, **f(x) = ______ . **

Try entering** f(x) = 2nroot((x - 1)^2,3) - 1 **which will show a cusp on the graph at $(1,-1)$ for** $f(x)=2\sqrt[3]{(x - 1)^2} - 1$**