Cosine is a trigonometric function describing the ratio of the adjacent side to the hypotenuse in a right triangle. It is often abbreviated cos.

2π radians is equivalent to one circle. The graph continues in that pattern.
Relation to secant
Cosine is a trigonometric function describing the ratio of the adjacent side to the hypotenuse in a right triangle. It is often abbreviated cos.

2π radians is equivalent to one circle. The graph continues in that pattern.