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Math Help - graphing [math]y=3cos(x+3pi)-2[/math]

  1. #1
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    graphing [math]y=3cos(x+3pi)-2[/math]

    hoping you can help me figure this out. graphing is a little hard for me at the moment.

    Find the Amplitude, the period and the phase shift for the following

    y=3cos(x+3pi)-2

    so far here are my answers

    Amp = |3| or 3

    period = 2pi/1 or 2pi

    and phase shift =  -3pi

    the question i have is how do I start graphing this?

    -4pi -3pi -2pi -pi 0 pi 2pi 3pi 4pi?

    thanks!
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  2. #2
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    Quote Originally Posted by rasczak View Post
    y=3cos(x+3pi)-2
    A major point of this type of problem is form you to figure out that things have relationships. Rather than start a new table, as if you know nothing, you are almost done.

    Graph y0 = cos(x)

    Graph y1 = 3cos(x) -- Just change the vertical limits from [-1,1] to [-3,3]. Done

    Graph y2 = 3cos(x) - 2 -- Just change the vertical limits from [-3,3] to [-5,1]. Done

    Graph y3 -- Oh, you're not going to make me do ALL the work, are you? You do this one.

    Of course, when you are done, you may wish to find the x- and y- coordinate axes. They did wander around a bit.
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  3. #3
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    Quote Originally Posted by rasczak View Post
    hoping you can help me figure this out. graphing is a little hard for me at the moment.

    Find the Amplitude, the period and the phase shift for the following

    y=3cos(x+3pi)-2

    so far here are my answers

    Amp = |3| or 3

    period = 2pi/1 or 2pi

    and phase shift =  -3pi

    the question i have is how do I start graphing this?

    -4pi -3pi -2pi -pi 0 pi 2pi 3pi 4pi?

    thanks!
    Attached is the graph. Use TKHunny's method to get it

    Also cos(x) is plotted for contrast
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  4. #4
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    Quote Originally Posted by TKHunny View Post
    A major point of this type of problem is form you to figure out that things have relationships. Rather than start a new table, as if you know nothing, you are almost done.

    Graph y0 = cos(x)

    Graph y1 = 3cos(x) -- Just change the vertical limits from [-1,1] to [-3,3]. Done

    Graph y2 = 3cos(x) - 2 -- Just change the vertical limits from [-3,3] to [-5,1]. Done

    Graph y3 -- Oh, you're not going to make me do ALL the work, are you? You do this one.

    Of course, when you are done, you may wish to find the x- and y- coordinate axes. They did wander around a bit.
    sorry. you lost me i'm going to go back over the basics and see what i'm missing here.
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  5. #5
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    sorry I finally got it somewhat figured out. what i had been meaning to ask was how my x axis was supposed to look.

    -4pi -3pi -2pi -pi 0 pi 2pi 3pi 4pi?

    Thanks for helping me figured out where I was supposed to start with regards to the y axis.
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  6. #6
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    Really, I mean physically relabel the x- and y- axes as necessary. It will hurt, but you CAN do it.
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