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Math Help - draw cos graph

  1. #1
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    draw cos graph

    hi,

    i need to draw these on to a graph:

    1. Y= cosx
    2. Y= cosx+1
    3. Y= cos(x+30)

    i can do 1 and i think i have done number 2 correct but i can't do number 3.

    here is what i have done for number 1 and 2, i have had a go at what i think number 3 would be:

    draw cos graph-1-2.jpg
    i have labled them on the side also.

    i think numbers 1 and 2 are correct but if they aren't please let me know and mainly is number 3 correct??

    thanks!!!!!
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  2. #2
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    The thing with your drawing of the functions is that you've just drawn straight lines. They should be curves. You should use a program that's a bit better than paint at drawing functions. I myself use graph 4.3. Look the functions up there.

    Anyways, it should be like this:

    graph one should look like a periodic curve that repeats itself every 360 degrees, i.e. it goes from 1 to -1 on the y-axis after 180 degrees, and then goes back to 1 etc, starting at the point (0,1).

    Graph two should look like graph one, except for the fact that it's displaced by 1 in a positive direction on the y-axis.

    Graph three should look like graph one also, but should be displaced by 30 degrees to the left.

    Best wishes, and good luck with trigonometry!
    Last edited by scounged; February 14th 2011 at 10:26 AM. Reason: I found an error in my initial post
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  3. #3
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    in my book i have them as curves but i wasn't able to do that on paint because i didn't want to do it free hand! so what i have draw for B or graph 2 is correct??
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  4. #4
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    e^(i*pi)'s Avatar
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    No, because you have negative values on it. y = \cos(x) +1 is the graph of \cos(x) moved up one unit on the y axis which means that while the range it 0 < \cos(x) + 1 < 2


    For the sake of completion I've added the graphs (in a spoiler). cos(x) is in green, cos(x)+1 is in blue and cos(x+30) is in orange

    nb: this graph is in radians (pi/6 = 30 degrees). pi/2 = 90 degrees, pi = 180 degrees, 3pi/2 = 270 degrees and 2pi = 360 degrees

    Spoiler:
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  5. #5
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    would this be it then?? (it is labeled 2)

    draw cos graph-1-2.jpg
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  6. #6
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    e^(i*pi)'s Avatar
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    Looks fine to me (aside from the technical issues of lines instead of curves of course)
    Last edited by e^(i*pi); February 14th 2011 at 11:30 AM. Reason: typo
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