## anonymous 3 years ago HEEELLLPPPP PLEASEEEE! A sound wave is modeled with the equation y =1/4 cos 2pi/3 theta a. Find the period. Explain your method. b. Find the amplitude. Explain your method

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1. anonymous

note that waves can be of general eq, y=r cos wt, where r is the amplitude, w the angular velocity and t is the time parameter.

2. anonymous

This looks like physics.

3. anonymous

well do you know the answer?

4. anonymous

Yes but just so you know. This is a physics question not mathematics.

5. anonymous

cross reference your eq with the general eq above.

6. anonymous

ok well can i have the answer?

7. anonymous

did you try to do it yourself first?

8. anonymous

yes and i am beyind confused :/

9. anonymous

what did you get? by the way, your equation didnot involve time ......

10. anonymous

cause thats not what it asked for i just need the period of the graph and what the amplitude would be you do this by using trig and i got the amplitude is 4 and the period is 2 but i dont think that is right

11. anonymous

$\omega = \frac{ 2\pi }{ T }$

12. anonymous

amplitude, A through a mathematical analysis, the amplitude is the highest/lowest point of the curve. $$y =\frac{1}{4}\cos \frac{2\pi}{3}{ \theta}$$ $$y' =-\frac{1}{4}(\frac{2\pi}{3})\sin \frac{2\pi}{3}{ \theta}$$ let y'=0, $$\sin \frac{2\pi}{3}{ \theta}=0$$ $$\theta=0$$ y=1/4=A you follow?

13. anonymous

kinda

14. anonymous

yup, now, $$y'=\omega$$ the period is the time for two wavecrest, i.e. two amplitude, also aka two y'=0 so you find the w for two successive max points and you'll get it.

15. anonymous

on second thought, where is the time parameter=.=