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.
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.
The dot product of two vectors over the product of their lengths gives this function of the angle between them.
cosine [accept cosine of x, with x being any letter]