The UNIT circle is a circle of radius 1 (*see red line from origin to edge of circle*). It can be divided into 4 quadrants (*labelled Q1-Q4 above*). Any point on the circle (*p*) can be described using Cartesian coordinates *(x,y*) or polar coordinates (cos, sin). Polar coordinates are found by creating a right-angled triangle by drawing a perpendicular line from the point p to the x-axis. The angle is the angle created as shown. Cos = x/1 = x, and Sin = y/1 = y, as shown above.

Thus **any point can be represented ** by **(cos, sin) **and the **sine and cosine of**** angle yields a corresponding number**. Remember that the sine, cosine and tangent of any angle is just a relationship between two numbers (and so a number).

© Copyright rmcstudy