Hello, I think I figured it out: one mohr's circle is plotted with x being normal strain and y being shear strain, and the other plot is the one I am used to: the shear stress on the y-axis and normal stress on the x-axis. So now all the equations make sense to me.
This isn't a problem assignment per-say, but for a lab calculation. In my mechanics of material's class, we learned that the radius of Mohr's circle is the maximum strain, but now in my application lab-based class, the video is saying the radius is equal to the maximum strain divided by 2. So...