Cosecant's Identity Crisis

Listen up, buttercup. This joke is all about wordplay, see? "C.S.C." sounds like "cosecant," which is a math thing in trigonometry. The punchline is that "cosecant" can't "remember" his own name, get it? It's like saying a dude forgot who he is, but instead of a dude, it's a math term. And you probably failed math class, which is okay, I guess.