Related to orthogonality

  • Thread starter EvLer
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  • #1
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In one of my hw problems we are asked to prove this:

|X + Y|^2 + |X - Y|^2 = 2|X|^2 + 2|Y|^2

It seems quite simple: I just expanded both of them (cancelled 2(X dot Y) terms) and came up with the expression on the right. Is there something I am missing or is it really that simple?

Thanks !
 

Answers and Replies

  • #2
Hurkyl
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It really is!
 
  • #3
mathwonk
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linear algebra makes many questions in geometry rather trivial. for this reason high schools should teach the subject, instead of calculus, where they usually do an extremely bad job.
 

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