Cosine - GCSE Maths Definition

Cosine is a mathematical term that comes up a lot in trigonometry. It's one of the basic functions used to relate the angles and sides of a right-angled triangle. In a right-angled triangle, the cosine of an angle is the length of the side next to the angle (called the adjacent side) divided by the length of the longest side (called the hypotenuse). So, cosine helps you figure out how the sides of a triangle are connected to its angles. You'll often see it written as "cos" followed by the angle you are talking about, like cos(θ). It's very useful for solving problems involving triangles, waves, and even circles!