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Example 3--Page 4
What we will do is multiply by 4 at the top and bottom, so it will cancel those s.
Next we want to combine these two terms to get one term (product) and angle . If we change to and combine the first and second terms, we have:
Please note that the Product-to-Sum formulas , and , and all help us to get angle . Now we have:
The identity has been proven.
From the second proof, we can see that we used a lot of proof strategies. They are all based on our idea--reduce the 3 differences. Our idea is simple but powerful.
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© Copyright 1998 LWR, ThinkQuest team 17119. All rights reserved.