what is the cosine function
The sine of one of the angles of a right triangle (often abbreviated sin) is the ratio of the length of the side of the triangle opposite the angle to the length of the triangle's hypotenuse. The cosine (often abbreviated cos) is the ratio of the length of the side adjacent to the angle to the length of the hypotenuse. And the tangent (often abbreviated tan) is the ratio of the length of the side opposite the angle to the length of the side adjacent.