Prove Triangle Inequality for Complex Numbers z1 and z2

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SUMMARY

The discussion focuses on proving the Triangle Inequality for complex numbers z1 and z2, specifically the inequality |z2| - |z1| ≤ |z2 - z1|. The user attempts to manipulate the expressions by squaring both sides but encounters difficulties in simplifying the resulting equations. A simpler approach is suggested, utilizing the established Triangle Inequality theorem: |z - w| ≤ |z| + |w|, which provides a more straightforward solution to the problem.

PREREQUISITES
  • Understanding of complex numbers and their properties
  • Familiarity with the Triangle Inequality theorem
  • Basic algebraic manipulation skills
  • Knowledge of squaring expressions and simplifying inequalities
NEXT STEPS
  • Study the Triangle Inequality theorem in the context of complex numbers
  • Practice algebraic manipulation of inequalities involving complex numbers
  • Explore geometric interpretations of complex number operations
  • Learn about other inequalities in complex analysis, such as the Cauchy-Schwarz inequality
USEFUL FOR

Mathematics students, educators, and anyone interested in complex analysis or inequalities in mathematical proofs.

stunner5000pt
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Edit: Nevermind i got it, thanks anyway

for complex numbers z1 and z2

prove that [tex]|z_{2}| - |z_{1}| \leq |z_{2} - z_{1}|[/tex]
the left hand side becomes
[tex]\sqrt{x_{2}^2 + y_{2}^2} - \sqrt{x_{1}^2 + y_{1}^2}[/tex]

the right hand side becomes
[tex]\sqrt{(x_{2} - x_{1})^2 + (y_{2} - y_{1})^2}[/tex]

now i tried squaring both sides and i get
left hand side
[tex]x_{2}^2 + y_{2}^2 + x_{1}^2 + y_{1}^2 - 2 \sqrt{(x_{2}x_{1})^2 + (x_{2}y_{1})^2 + (x_{1}y_{2})^2 + (y_{1}y_{2})^2}[/tex]

right hand side
[tex](x_{2} - x_{1})^2 + (y_{2} - y_{1})^2[/tex]
i put the two of them not equal to eah other and reduce and i ended up with
[tex]x_{2}^2 y_{1}^2 + x_{1}^2 y_{2}^2 \neq 2x_{1} x_{2} y_{1} y_{2}[/tex]
im stuck now...

please help
is there a simpler... less tedious way of doing this... by the way?
 
Last edited:
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The less tedious way is to use the triangle inequality: [itex]|z-w|\leq |z|+|w|[/itex]
 

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