1# Preliminary topics 2 3## Circular functions 4 5$\sin \theta$ - $y$-coord on unit circle 6$\cos \theta$ - $x$-coord on unit circle 7$\tan \theta = {\sin \theta \over \cos \theta}$ 8 9$1^\text{c}= {180^\circ \over \pi} \quad \text{or} \quad 1^\circ = {\pi^\text{c} \over 180}$ 10 11period = $2 \pi \over n$ 12 13## Sine and cosine rules 14 15### Sine rule 16 17$${a \over \sin A}={b \over \sin B}={c \over \sin c}$$ 18 19### Cosine rule 20 21$$a^2=b^2 - 2bc \cos A$$ 22 23## Geometry 24 25### Parallel lines 26 27If parallel lines are crossed by transversal: 28 29- alternate angles are equal 30- corresponding angles are equal 31- co-interior angles are supplementary 32 33{#id .class width=40%} 34 35### Angles in a polygon 36 37Sum of interior angles of $n$-sided polygon is $(n-2) \times 180^\circ$ 38 39### Circle geometry 40 41-  The angle at the centre of a circle is twice the angle at the circumference subtended by the arc 42-  the angle in a semicircle is a right angle 43-  angles in the same segment of a circle are equal 44- ![]()