How to Determine the Sign of the Doppler Shift?

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    Doppler System
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The discussion revolves around understanding how to determine the sign of the Doppler shift. It highlights that both the problem statement and the answer imply that the sign indicates the direction of relative velocity. However, the main question is about the method for determining the sign of the shift itself. Clarification is sought on the specific approach to ascertain this sign. The conversation emphasizes the need for a clear explanation of the Doppler shift's sign determination.
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Homework Statement
If the velocity of the target is positive, ∆𝑓 > 0.
If the velocity of the target is negative, ∆𝑓 < 0. How to identify the sign of ∆𝑓 in Doppler system?

Did I answer it correctly? thank you
Relevant Equations
I put that in the picture below
Screen Shot 2022-06-08 at 16.46.17.png

answer:
Screen Shot 2022-06-08 at 18.02.51.png
 
Last edited:
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I don't know what answer is wanted. As I read it, both the problem statement and your answer assert that the sign of the shift tells you whether the relative velocity is positive or negative. But the question is asking how you determine the sign of the shift, no?
 

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