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emilyliv emilyliv
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3 years ago
determine the equation for each sinusoidal function. ii)
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wrote...
#1
Educator
3 years ago
Answer for ii)


emilyliv Author
wrote...
#2
3 years ago
the answer from the textbook is y= -0.5cos(120x) + 1, and also we don't use pi for this course.
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#3
Educator
3 years ago
Yes, ignore -1 as "a", should be -0.5. Sorry, I didn't zoom in all the way. Another thing to mention is that I used radians for my answer, while the textbook answered in degrees (it wasn't mentioned so I used radians instead).

Here's the method I used, please watch these, they're really helpful when understanding this:
emilyliv Author
wrote...
#4
3 years ago Edited: 3 years ago, emilyliv
thank you, and just making sure for i) the horizontal translation in degrees would be (x - 4)? bc 2 other websites said it was either (x - 1) or (x + 2), so I got confused. And for iii) wouldn't it be cosine rather than sine?
wrote...
#5
Educator
3 years ago
I got:

Radians: \(y=3\cos \left(\frac{\pi }{3}x+\frac{2\pi }{3}\right)+5\)

Or...

Degrees: \(y=3\cos (60° x+120° )+5\)

factor out the 60... \(y=3\cos (60\left(x+2\right))+5\)

So I'm assuming x+2

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bc 2 other websites said it was either (x - 1) or (x + 2)

Which websites?
wrote...
#6
Educator
3 years ago
What I find strange about this question is that they x-axis is in 1,2,3,4,5 yet they want the answer in degrees. It should be radians, not degrees unless they made the x-axis in degrees as well, makes no sense.
emilyliv Author
wrote...
#7
3 years ago
thanks again, and the websites I use are slader and prepanywhere, but sometimes they can be inaccurate.
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#8
Educator
3 years ago
Never heard of that site before.

You sure you understand this stuff though?
emilyliv Author
wrote...
#9
3 years ago
yes, just also wanted to know for iii) if it was either cosine or sine, because it said it was cosine from the textbook, but I'm pretty sure its sine.
wrote...
#10
Educator
3 years ago
emilyliv, any sinusoidal graph can be represented in either sine of cosine, so it doesn't matter which one you choose.

In other words, I could represent it as cosine or sine, and it'll look identical
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