In the unit circle the hypotenuse of the triangle formed is equal to radius of circle , which = 1. The point on the circle formed by the intersection of the hypotenuse is (cos q , sin q) where q is the angle between the x axis and the hypotenuse. As the hypotenuse = 1 the opposite and adjacent sides of the triangle < 1 so sin and cos of q must both be <= 1.
A vertical line is any line parallel to the vertical direction. A horizontal line is any line normal to a vertical line. Horizontal lines do not cross each other.
