Note, the $y-$axis is moved so the equation of a line $)=(mx+b$ has the $y-$intercept as zero. This moving of the $y-$axis will change the limits of integration.

Using the integration method, derive moment of inertia equation for a triangle about the x $-$axis $($the bottom$)$

Using the integration method derive moment of inertia equation for a triangle about its X Centroid Axis. Notice how the axis had to move to the centroid location