# Exercise 6: Plotting a derived variable 
**(10 minutes)**

Revise `AnalyzeVariables.py` to make a histogram of the variable **`pt`**.
Don't forget to label the axes; remember that the momenta are in *GeV*.

:::{admonition} Cheating
:class: note

If you want to figure out what the bin limits of the histogram should
be, I'll permit you to "cheat" and use the following command
interactively:

    tree1.Draw("sqrt(px*px + py*py)")
:::