**Sine and Cosine Formulae**

sin x = sin (180 - x)

cos x = -cos (180 - x)

**The Sine Rule**

This works in any triangle:

__ a __ = __ b __ = __ c __

sinA sinB sinC

alternatively, __sinA__ = __sinB__ = __sinC__

a b c

NOTE: the triangle is labelled as follows:

**The Cosine Rule**

c² = a² + b² - 2abcosC

which can also be written as:

a² = b² + c² - 2bccosA

This also works in any triangle.

**The area of a triangle**

The area of any triangle is ½ absinC (using the above notation)

This formula is useful if you don't know the height of a triangle (since you need to know the height for ½ base × height).

Trigonometry

Trigonometry

Trigonometry

Trigonometry

Trigonometry