### Unit Circle - Sin and Cos

In trigonometry, a unit circle is the circle of radius one centered at the origin $(0, 0)$ in the Cartesian coordinate system. Let a line through the origin, making an angle, of $\theta$= with the positive half of the x-axis, intersect the unit circle. The x-coordinates and y-coordinates of this point of intersection are equal to $\cos(\theta)$ and $\sin(\theta)$, respectively. See Wikipedia.