Proving Identities

Strategy, and testing claims

An interactive lesson with 6 steps, about 5 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• Transform one side into the other; rewrite in sin and cos.
• Graphs and test values catch false claims; one counterexample disproves.
• Factoring, Pythagoras and double angles do most of the work.

Steps

1. How to prove an identity
2. Build the proof
3. Test by graphing
4. A counterexample
5. Which is an identity?
6. Factor first