My attempt at a sexy math joke
A sine wave and a cosine wave are trying to have a baby. They are deeply religious so the only position they are able to do is missionary. After many attempts they think they might have conceived a child. The cosine wave grabs a pregnancy test, goes into the bathroom, and comes out a couple of minutes later. The sine wave says “well is it negative or positive?” and the cosine wave says “no, it’s tangent.”