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Vector Analysis

  1. Dec 15, 2013 #1


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    1. The problem statement, all variables and given/known data

    If a and b are vectors such that|a|=|b|=|a-b|, what is then the angle between a and b? What changes for |a|=|b|=|a+b|

    2. Relevant equations

    3. The attempt at a solution

    |a|=|b| ⇔ a=b ∴ a=b ⇔|a-b|=0 ...identity of discernibles

    angle between them is then 0.

    |a|=|b|=|a+b| ⇔ |a+b| = |2a| or |2b| = |2||a| = 2|a|.

    The magnitude of a or b changes but angle between a and b is 0 since a=b.

    Is this correct logic?
  2. jcsd
  3. Dec 15, 2013 #2


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    No, it's not. |a|=|b| doesn't imply a=b. For example, |(1,0)| = |(0,1)|.
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