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Reverse triangle inequality for n real numbers

  1. Nov 3, 2008 #1
    I have been trying the proof of the reverse triangle inequality for n+1 real numbers:

    |x-y1-y2-y3-....-yn| [tex]\geq[/tex] | |x| - |y1| - |y2| - |y3| - ....-|yn| |

    I know the proof of the reverse triangle inequality for 2 real numbers and the triangle inequality for n numbers. can somebody help ?
  2. jcsd
  3. Nov 3, 2008 #2
    this inequality isn't even true, take x=0 for instance, and y1=1, y2=-1, y3=1...
    when n is even, you get zero on left hand side and n on the right hand side.
  4. Nov 4, 2008 #3
    There goes 1 hour trying to prove something which is easily disproved. It was one exercise in a Real analysis book. Well atleast I learnt how to be critical of everything now ^^
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