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skullofreak Group Title

help!!

  • 7 months ago
  • 7 months ago

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  1. skullofreak Group Title
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    • 7 months ago
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  2. skullofreak Group Title
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    how do I write the equation of the graph?

    • 7 months ago
  3. alffer1 Group Title
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    Tell me what the graph of y = cos x looks like.

    • 7 months ago
  4. skullofreak Group Title
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    its (0,1) (pi,-1) (2pi,1) (3pi,-1) etc

    • 7 months ago
  5. skullofreak Group Title
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    but with the dots in um the up and down motions (from half of 0 and pi , pi and 2pi,

    • 7 months ago
  6. alffer1 Group Title
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    So what is the difference between this one and cosx?

    • 7 months ago
  7. skullofreak Group Title
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    its sin ? and the graph is given but I don't know how to get an equation

    • 7 months ago
  8. skullofreak Group Title
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    nvm its cos

    • 7 months ago
  9. ranga Group Title
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    The sine function is zero when x = 0. A cosine function is 1 when x = 0. So we need to choose the acos(bx) here. a is the amplitude. Amplitude is how much above or how much below the mean line (which is x axis here) the curve swings. Could you figure out the amplitude from the diagram?

    • 7 months ago
  10. skullofreak Group Title
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    a = 3

    • 7 months ago
  11. skullofreak Group Title
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    so y = 3cos.. bx

    • 7 months ago
  12. ranga Group Title
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    Yes. a = 3. So the equation is y = 3cos(bx). We still need to figure out b. The period of a cosine or a sine function is how long before the curve repeats itself. Could you look at two successive peaks in the diagram and figure out after how much x the function repeats itself?

    • 7 months ago
  13. skullofreak Group Title
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    every 3pi?

    • 7 months ago
  14. skullofreak Group Title
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    or every 6pi/2?

    • 7 months ago
  15. ranga Group Title
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    No. The curve attains a peak at x = 0. The next peak occurs at x = 6pi. The period is how much x has passed before the curve starts to repeat itself. So what is the x distance between peak-to-peak?

    • 7 months ago
  16. skullofreak Group Title
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    6pi/2

    • 7 months ago
  17. ranga Group Title
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    No. At x = 0, first peak. At x = 6pi the next peak. The difference in x is: 6pi - 0 = 6pi. Every 6pi the curve repeats itself. You can take the distance between two successive low points also and it will still be 6pi. So the period of this curve is 6pi.

    • 7 months ago
  18. skullofreak Group Title
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    OH

    • 7 months ago
  19. skullofreak Group Title
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    y=3cos (6pi)x ?

    • 7 months ago
  20. ranga Group Title
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    The formula for the period of cos(bx) is: Period = 2pi / b Looking at the graph we found the period to be 6pi. Plug that into the formula: 6pi = 2pi / b Find b.

    • 7 months ago
  21. skullofreak Group Title
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    2pi/6pi = pi/3pi

    • 7 months ago
  22. ranga Group Title
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    The pi will cancel out. so b = ?

    • 7 months ago
  23. skullofreak Group Title
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    yes sorry

    • 7 months ago
  24. skullofreak Group Title
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    1/3

    • 7 months ago
  25. ranga Group Title
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    Yes. Put them all together and the curve represented in the graph is: y = 3cos(1/3*x)

    • 7 months ago
  26. skullofreak Group Title
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    okay thank you!! a lot!

    • 7 months ago
  27. ranga Group Title
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    You are welcome.

    • 7 months ago
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