### 3.2. Basic trigonometry

Before each question make sure calculator is in correct setting: degrees or radians?

#### Right-angle triangle (triangle with 90° angle)

#### Non-right angle triangles

Use this rule when you know: 2 angles and a side (not between the angles) or 2 sides and an angle (not between the sides).

* Cosine rule*: c

^{2}= a

^{2}+ b

^{2}− 2ab cosC

Use this rule when you know: 3 sides or 2 sides and the angle between them.

* Area of a triangle*: Area = ½ ab sinC

Use this rule when you know: 3 sides or 2 sides and the angle between them.

#### Three-figure bearings

Direction given as an angle of a full circle. North is 000° and the angle is expressed in the clockwise direction from North. So East is 090°, South is 180° and West 270°.

### 3.3. Circular functions

* Trigonometric function* y = a sin(bx + c) + d

**Trigonometric identities**