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).