Given the task definition and input, reply with output. In this task you will be given a text passage from a trivia quiz. You should choose the category this question belongs to from these categories: History, Science, Social Science, Fine Arts, Literature. You can only choose one category, so if in doubt, please choose the closest match.

The dot product of two vectors over the product of their lengths gives this function of the angle between them. A law named for this function generalizes the Pythagorean theorem to non-right triangles; it uses two sides of a triangle and the included angle to find the length of the third side. (*) For 10 points, name this trigonometric ratio commonly calculated as "adjacent over hypotenuse" in right triangles.
Science