1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Vector proof - four points in space

  1. May 15, 2012 #1
    The problem is: A, B, C, D are any four points in space. If M and N are the mid-points of AC and BD, show that AB + CB + CD = 4MN.

    I'm not quite sure where to start. Could someone please help me?
  2. jcsd
  3. May 15, 2012 #2
    I'm not sure that the problem is correct. Suppose that A,B,C,D are the four corners of a square. In this case, M and N would both be the center of the square. This would make MN=0
  4. May 15, 2012 #3


    User Avatar
    Science Advisor
    Homework Helper

    welcome to pf!

    hi nc01! welcome to pf! :smile:
    ?? :confused:

    i think you need an AD in there …

    AB + AD + CB + CD = 4MN :wink:
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Threads - Vector proof four Date
Prove this is a right triangle in a sphere Sep 5, 2016
Help with vector proof May 1, 2016
Proof: Max number of Linearly Independent Vectors Sep 13, 2015
Vectors product proof Mar 6, 2014
Vectors mixed product proof Mar 5, 2014