I don't see the point of plotting the derivative on the same graph as the function, and I think this will confuse students who are exposed to the derivative for the first time. Functions and their derivatives have different units, and only rarely do they need to be plotted together.
Once it is understood that the derivative is an expression that gives us the slope of the tangent at any point of the original graph, then it may be interesting to remark that the derivative is in fact a function, and may therefore be plotted, or differentiated, or set equal to zero to find its roots.
If you read his previous post "Hairy Questions" he warns that the next few posts are for up and coming AP calculus students. It is assumed that they already have a sense of what derivatives are and what not so I think it is justified.
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[ 2.8 ms ] story [ 16.6 ms ] threadOnce it is understood that the derivative is an expression that gives us the slope of the tangent at any point of the original graph, then it may be interesting to remark that the derivative is in fact a function, and may therefore be plotted, or differentiated, or set equal to zero to find its roots.