What does this vector equal to?

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SUMMARY

The discussion centers on proving the equation |\vec{A}|² + |\vec{B}|² = \frac{1}{2}(|\vec{A} + \vec{B}|² + |\vec{A} - \vec{B}|²). Participants suggest using the definition of modulus and expanding the right-hand side to approach the proof. The triangle inequality is mentioned but deemed irrelevant since the problem requires establishing an equality rather than an inequality. Clear explanations and step-by-step guidance are requested for solving the problem.

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Homework Statement


Prove that |[tex]\vec{A}[/tex]|2+|[tex]\vec{B}[/tex]|2 equals to [tex]\frac{1}{2}[/tex](|[tex]\vec{A}[/tex]+[tex]\vec {B}[/tex]|2+|[tex]\vec{A}[/tex]-[tex]\vec{B}[/tex]|2)

Homework Equations


Perhaps the triangle inequality? I am not sure.

The Attempt at a Solution


I have no idea how to approach this question. Please help me with clear explanations. Thank you.
 
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Hi Cuisine123! :smile:

Use the definition of modulus: |A + B|2 = (A + B).(A + B) etc :wink:
 
Perhaps not the triangle inequality. That is an inequality. You are looking for an equality.

Have you tried expanding the right hand side?
 

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