Solving Eigenvalues: Complex Numbers Solutions

  • Context: Undergrad 
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Discussion Overview

The discussion centers on the calculation and representation of eigenvalues involving complex numbers, specifically focusing on converting complex numbers to their polar form. Participants explore the angles associated with these representations and the rules for adjusting negative angles.

Discussion Character

  • Technical explanation, Mathematical reasoning, Debate/contested

Main Points Raised

  • One participant presents eigenvalues λ1=i-1 and λ2=i+1 in polar form as √2 e^i(3∏/4) and √2 e^i(∏/4), respectively.
  • Another participant suggests converting the numbers to their polar form as a method for understanding the eigenvalues.
  • A participant questions the angle associated with λ1, proposing that it could be -∏/4 and asks if a rule exists for adjusting negative angles.
  • One participant corrects the angle for λ1, stating that if it were -∏/4, the corresponding expression would be 1 - i, implying a misunderstanding.
  • Another participant adds that one can add 2∏ to a negative angle, clarifying that adding ∏ would result in multiplying by -1.

Areas of Agreement / Disagreement

The discussion contains multiple competing views regarding the correct angle for λ1 and the rules for adjusting negative angles, indicating that there is no consensus on these points.

Contextual Notes

Participants express uncertainty about the correct representation of angles in polar form and the implications of adjusting negative angles, highlighting potential misunderstandings in the conversion process.

izzy93
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I have solutions for eigenvalues to be

λ1=i-1 = √2 e^i(3∏/4) and
λ2=i+1 =√2 e^i(∏/4)

How do you go from the i-1 to the next bit for both?

Thanks
 
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Thanks,

Just wondering for λ1=i-1 = √2 e^i(3∏/4) , I get the angle phi to be -∏/4 so if the angle is negative do you take it as a rule to add on ∏?
 
izzy93 said:
Thanks,

Just wondering for λ1=i-1 = √2 e^i(3∏/4) , I get the angle phi to be -∏/4 so if the angle is negative do you take it as a rule to add on ∏?

The angle isn't -∏/4.
If it were, the corresponding expression would be 1 - i.
 
izzy93 said:
Thanks,

Just wondering for λ1=i-1 = √2 e^i(3∏/4) , I get the angle phi to be -∏/4 so if the angle is negative do you take it as a rule to add on ∏?

You can add 2∏. When you add ∏, you are multiplying by -1.
 

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