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JenniferSmart1
 2 years ago
how do I graph \[y=3cos(3x)\]?
I know that 3 is the amplitude
I know that the graph will be upside down.
I know that the period is \[\frac{2\pi}{3}\]
JenniferSmart1
 2 years ago
how do I graph \[y=3cos(3x)\]? I know that 3 is the amplitude I know that the graph will be upside down. I know that the period is \[\frac{2\pi}{3}\]

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stamp
 2 years ago
Best ResponseYou've already chosen the best response.1Copy the image and begin by marking your amplitude, the highest and lowest point of the wave.dw:1360290026921:dw

JenniferSmart1
 2 years ago
Best ResponseYou've already chosen the best response.1dw:1360290074055:dw

stamp
 2 years ago
Best ResponseYou've already chosen the best response.1now label \[(\frac{2\pi}{3},f(\frac{2\pi}{3}))\]this point is the end of your period.

JenniferSmart1
 2 years ago
Best ResponseYou've already chosen the best response.1dw:1360290246963:dw

stamp
 2 years ago
Best ResponseYou've already chosen the best response.1\[f(x)=3cos(3x)\]\[f(\frac{3\pi}{2})=3cos(3(\frac{3\pi}{2}))=3cos(9\pi/2)\]

JenniferSmart1
 2 years ago
Best ResponseYou've already chosen the best response.1it's \[\frac{2\pi}{3}\] for the period

stamp
 2 years ago
Best ResponseYou've already chosen the best response.1@JenniferSmart1 My fault. You evaluated it correctly, I would have gotten 0 for f(3pi/2) while f(2pi/3) is 3. Ok, so now can you finish the graph from here? So far you have done an excellent job.

JenniferSmart1
 2 years ago
Best ResponseYou've already chosen the best response.1dw:1360290496676:dw

stamp
 2 years ago
Best ResponseYou've already chosen the best response.1Could we label the highest point (x, f(x)) if we were asked?

JenniferSmart1
 2 years ago
Best ResponseYou've already chosen the best response.1Let's see \[( \frac{\pi}{3} , 3)\] because \[\frac{2\pi}{3\cdot2}\]

stamp
 2 years ago
Best ResponseYou've already chosen the best response.1Ok! I think your graph seems pretty complete, well done. Here is the actual graph for reference http://www.wolframalpha.com/input/?i=3cos%283x%29

JenniferSmart1
 2 years ago
Best ResponseYou've already chosen the best response.1I'm guessing because its half way between 2pi/3
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