Physics: Three Ways to Calculate the Work Done by the Normal Force

This is part of my classical mechanics series. You can find all my videos in the series in the following playlist.

What is the work done by friction as a block slides down an incline? In this case, I'm going to calculate this THREE ways. First, by assuming constant forces and paths. Second, creating a line integral. Third - modeling a block on a plane with springs to calculate the vector normal force.

Here is the python code

[fizixx]

At 6:35, where you have the integral from x1 to x2 of 0*dx, instead of zero wouldn't it result in: A constant C|[x1, x2] ===> x2 - x1?