# Thread: Oscilloscope problem

1. ## Oscilloscope problem

Please can anyone help me with this problem.

Question is what is formula for X and Y if this is picture on oscilloscope?

Thanks!

2. Originally Posted by miro
Please can anyone help me with this problem.

Question is what is formula for X and Y if this is picture on oscilloscope?

Thanks!
It appears to be an ellipse centred at the origin, so its equation will be of the form $ax^2+bxy+cy^2=1$, where a, b and c are constants whose values will depend on the dimensions and orientation of the ellipse.

3. Originally Posted by miro
Please can anyone help me with this problem.

Question is what is formula for X and Y if this is picture on oscilloscope?

Thanks!
$x=5 \sin(\omega t)$

$y=4 \sin(\omega t + \phi)$

The relative phase difference $\phi$ will determine the orientation of the ellipse, and from the display you cannot determine the frequency $\omega$

CB

4. Thanks! CaptainBlack , can you tell me how did you get this. My only clue how to read this picture is that arcsin(a/b) is phase angle between x and y.

5. Originally Posted by miro
Thanks! CaptainBlack , can you tell me how did you get this. My only clue how to read this picture is that arcsin(a/b) is phase angle between x and y.
Its the Lissajous figure you get when you apply a sin wave to the x input and another sine wave (different amplitude and phase but same frequency) to the y input. The amplitude of the x-wave is the maximum x value that the figure achives, and of the y-wave is the maximum y value.

CB