The unit circle
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).
Solving problems using the unit circle (i)
Solving problems using the unit circle (ii)
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