Express y(t) as a function of x(t)

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Homework Statement


Express y(t) as a function of x(t).

https://www.physicsforums.com/attachment.php?attachmentid=61309&d=1378005939

Homework Equations




The Attempt at a Solution


Transformations:
-x(t)
0.5x(t)
x(2t)
x(t-2)
x(t)+1.5

∴y(t) = -0.5x(2t-4)+1.5

Here is the plot:

Two stacked plots sharing a time axis from 0 to 9: top shows x(t) rising linearly from 0 to 5 over 0 to 2, dropping to -3, flat until 4, rising to 0 at 5, then flat; bottom shows y(t) flat at 1.5, falling to -1 between 2 and 3, jumping to 3 at 4, falling to 1.5 at 4.5, then flat.


As seen in the plot above, it is different from the figure in the book (P2.4(b)) on the time interval 4 < t < 5. Where am I going wrong?

Thanks!
 
Attachments
  • Two stacked plots sharing a time axis from 0 to 9. Top: x(t) rises linearly from 0 to 5 over 0 to 2, drops to -3, stays flat to 4, rises to 0 at 5, then stays at 0. Bottom: y(t) is 1.5 to t=2, falls linearly to -1 at t=3, jumps to 3 at t=4, falls to 1.5 at t=4.5, then stays at 1.5.
    img2.png
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  • Two piecewise-linear plots against t: (a) x(t) rising from 0 to 5 at t=2, dropping to -3, flat to t=4, rising to 0 at t=5, then zero; (b) y(t) flat at 1.5 to t=2, falling to -1 near t=3, jumping to 3, falling to 1.5 at t=5, then flat.
    img.jpg
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Last edited:
I just noticed that the time scale for 4 < t < 5 remains the same for the figure in the book. I know the time scale is compressed by 0.5 up until t = 4. So, is the book's figure supposed to look like my plot instead? It seems impossible to express y(t) as a function of x(t) if I use the figure in the book.