## Trigonometry

### Introduction

###### Three common ratios are described below:    ### 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, thenby 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 (ii)  #### LC Solution ### Trig formulae questions  #### L.C. solutions   ### Trigonometric Graphs #### L.C. solution ### Sine & Cosine rules  