As Joi Ito said, too funny not to blog. I know it’s old, but I still laughed out loud:
After explaining to students through various lessons and examples that
[tex]\displaystyle \lim_{x\to 8} \frac{1}{x-8} = \infty[/tex].
I tried to check if she really understood that, so I gave her a different example; the result of which was:
[tex]\displaystyle \lim_{x\to 5} \frac{1}{x-5} = \rotatebox{90}{5}[/tex].
Hah!