Home Light Version Normal Version Search | BBS | Guest Book | Site Map | Help | Contact us | About us

### [Index]

Introduction
Essence
Memorizing
 How to memorize Basic Formulas Sum and Difference Formulas Double & Triple Angle Formulas Half Angle Formulas Product to Sum Formulas Sum to Product Formulas All Formulas
Understanding
 Page 1 Page 2 Page 3 Page 4 Page 5
Summarizing
 Page 1 Page 2
Examples
 Examples Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 General ideas
Exercises
Final thoughts
Page 1 | Page 2 | Proof(s)

### Example 7--Page 2

We are very happy that we get this far. Using our compare strategy, we know that the terms in the parenthesis should equal to . In which there is no , using (which we can get from the condition) we can transform to . Using the same way as we did above, we get:

Converting sum to product, we have:

The identity has been proven.

This is a really good problem, once you understand the process of solving this identity, and you know the strategies, you are in very good shape. Try to think why we take steps like that. You will be surprised at how far you have already come.