And I thought I’ve seen everything when I saw how one student used the product rule to get the derivative of $\cos x$: $(\cos x)^\prime = \cos 1 + x \sin$.

Hell, it’s even worse than my previous student, who drew the shadow of the person between the person and the sun.

I rolled on the floor when I read this statement on at least 3 papers I’m checking right now:

Using the divergence test, the series is absolutely convergent.

Come on. There must be a reason why the divergence test was called the divergence test. I wonder, where did they learn that? I certainly don’t remember saying it in class.