1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Sinusoidal Graph - sub intervals

  1. Mar 16, 2011 #1
    1. The problem statement, all variables and given/known data

    I can find the graphs amp and period. The only problem is finding the sub points or sub intervals. Say...

    Y = 3 sin (4x)
    Amp = 3
    Period = 2pi/4 = pi/2

    But.. don't know how to get the key points of the sub interval. The text book says I have to divide interval [0, pi/2] into four sub intervals Each of length pi/2 divided by 4. Then they got (0,0), (pi/8, 3), (pi/4, 0), (3pi/8, -3), (pi/2, 0) I don't understand how they got these. Thanks

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Mar 16, 2011 #2


    User Avatar
    Homework Helper

    Draw the base graph y=sin(x) with [itex]0\leq x\leq 2\pi[/itex], It has a value of 0 at [itex]x=0,\pi,2\pi[/itex] and a value of 1 and -1 at [itex]x=\pi/2, 3\pi/2[/itex] respectively.
    Basically, every sine graph of the form [itex]y=Asin(Bx)[/itex] will still have this same shape, but the amplitude (A) and period (B) will be different from the base graph y=sin(x).

    What you should take away from this is that if the period of sin(x) is [itex]2\pi[/itex], then in between the two ends of the period 0 and [itex]2\pi[/itex] which is [itex]\pi[/itex], it will also be 0, and in between 0 and its half way mark which is [itex]\pi[/itex] we get the value of its amplitude (in this case 1), and between the half way mark and the end, [itex]\pi[/itex] and [itex]2\pi[/itex] we get the negative of its amplitude, -1.
  4. Mar 16, 2011 #3
    Thanks, I know that but I don't know how to get the points in between the sin graph

    I know if period = 2 pi then the middle point would me pi, but what if it has a different period. I don't know what to label on the graph on the middle part.
    Last edited: Mar 16, 2011
  5. Mar 16, 2011 #4


    User Avatar
    Homework Helper

    If the period is [itex]2\pi[/itex] then middle is half of that [tex]\frac{2\pi}{2}=\pi[/tex]. If the period is some number x then the middle is x/2.
  6. Mar 16, 2011 #5
    Ahhh I see now. Thank you my friend.
  7. Mar 16, 2011 #6


    User Avatar
    Homework Helper

    Good luck! :smile:
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Sinusoidal Graph - sub intervals
  1. Sinusoidal functions (Replies: 2)

  2. Open interval (graph) (Replies: 6)