# Sine & cosine formulae resources

### Video (2)

a cos x + b sin x = R cos(x-alpha) - an Animation

This mathtutor animation shows how the formula a cos x + b sin x = R cos(x-alpha) may be derived using right angled triangles. This resource is released under a Creative Commons license Attribution-Non-Commercial-No Derivative Works and the copyright is held by Skillbank Solutions Ltd.

Triangle formulae

A common mathematical problem is to find the angles or lengths of the sides of a triangle when some, but not all, of these quantities are known. It is also useful to be able to calculate the area of a triangle from some of this information. (Mathtutor Video Tutorial)
This resource is released under a Creative Commons license Attribution-Non-Commercial-No Derivative Works and the copyright is held by Skillbank Solutions Ltd.