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I have exam tommorow and cant get this figured out :( dont blame me but please answer this question. I Want to simplify this term:

3 times ((e topowerof 5jt) + (e topowerof -5jt))

Thanks.

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For future reference we have the MathJax LaTeX rendering engine active on the site so that you could write $3 e^{5jt} e^{-5jt}$ and get $3 e^{5jt} e^{-5jt}$. – dmckee♦ Dec 30 '12 at 23:39

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1 Answer

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$6\cos(5t)$; use Euler's formula for sine and cosine.

$\exp(i*\theta)=cos(\theta)+i*sin(\theta)$

From this you can show, $$sin(\theta)=(1/2i)*(\exp(i*\theta)-\exp(-i*\theta))$$ $$cos(\theta)=(1/2)*(\exp(i*\theta)+\exp(-i*\theta))$$

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Thanks, I know the answer is 2sin(3t) as it is on my teachers handout...can you please say how to get to this number? what steps should be done? I know eulers formulas but cant apply it here. – Sean87 Jun 21 '11 at 0:56
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It's not $2\sin(3t)$; it's what New Horizon said. – Ted Bunn Jun 21 '11 at 14:31

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