## anonymous 3 years ago how do i prove this using trig identity: (2sinx+3cosx)^2+(3sinx-2cosx)^2=13

1. anonymous

i did this on my calculator type it in your calulator just as your type on here tell me what you get

2. anonymous

i have to prove it using trigonometric identity without a calculator

3. anonymous

First, use foil to expand them. Then use the following identity $\sin^2(\theta)+\cos^2(\theta)=1$

4. anonymous

what do i do with the leading coefficients?

5. anonymous

Factor them out.

6. anonymous

What did you get?

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