Cosine Sum Identity

Click the Next button to walk through a proof of cos(A+B)=cos(A)cos(B)-sin(A)sin(B).
Use the Reset button to return to the start at any point.

This is a Java Applet created using GeoGebra from www.geogebra.org - it looks like you don't have Java installed, please go to www.java.com

Questions:

1. How could we find sin(A+B) using this construction?

2. What would we need to do differently for cos(A-B)?

Dixie Christensen, 25 November 2013, Created with GeoGebra