Signals and Systems Theory Question

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Discussion Overview

The discussion revolves around the conversion of trigonometric functions to exponential forms using Euler's identity within the context of a signals and systems theory problem. Participants explore the steps involved in this transformation and the underlying theoretical principles.

Discussion Character

  • Homework-related
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant questions the validity of directly equating 2.5cos(3t) with 2.5e^(3jt) and seeks clarification on the transformation process.
  • Another participant suggests rewriting sin(x) and cos(x) in terms of Euler's identity and substituting these into the original equation to establish equivalences.
  • A participant references the definition of cos(theta) as 1/2(e^j(theta) + e^-j(theta)) and expresses confusion about how this relates to the previous claims.
  • There is a suggestion to combine coefficients of e^(j3t) and e^(-j3t) to clarify the transformation process.
  • One participant expresses understanding after receiving clarification on the use of Euler's identity.

Areas of Agreement / Disagreement

Participants exhibit disagreement regarding the direct equivalence of trigonometric and exponential forms, with some expressing confusion and others providing clarification. The discussion remains unresolved as participants explore different approaches to the problem.

Contextual Notes

There are limitations in the assumptions made about the transformation process, and the discussion does not resolve the mathematical steps involved in the conversion from trigonometric to exponential forms.

OmniNewton
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Homework Statement


7e9b8c745e2fc43b704bfca37ef3a2e7.png
[/B]
920158fcddac0baf83416fb34e1885b5.png

How are we able to go from the first line to the second line and then the second line to the third?

Homework Equations


Euler Identity: e^j(theta) = cos(theta) +jsin(theta)

The Attempt at a Solution


This problem is more about preliminary theory in my opinion so I tried understanding how they converted the problem from trigonometric functions to exponential by analyzing the Euler Identity.
 
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Rewrite sin(x) and cos(x) in terms of the Euler identity, substitute in the original equation, and force equivalences.
 
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rude man said:
Rewrite sin(x) and cos(x) in terms of the Euler identity, substitute in the original equation, and force equivalences.

Thank you for the response sir but I really do not see how that works. How can one simply say that 2.5cos(3t) = 2.5e^(3jt). I thought cos(theta) = 1/2(e^j(theta) + e^-j(theta)) determined by the subtraction of 2 mcclauirin series.
 
OmniNewton said:
Thank you for the response sir but I really do not see how that works. How can one simply say that 2.5cos(3t) = 2.5e^(3jt).
You can't.
I thought cos(theta) = 1/2(e^j(theta) + e^-j(theta))
Right. Use that and the similar expression for sin(theta) and combine coefficients of ej3t and e-j3t.
 
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rude man said:
You can't. Right. Use that and the similar expression for sin(theta) and combine coefficients of ej3t and e-j3t.
Oh I see! That makes a lot of sense thank you kindly.
 

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