1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    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!

Homework Help: Dot Product help

  1. Jul 28, 2006 #1
    -Use the dot product to prove that the quadrilateral with vertices A(-4,1) B(4,5) C(7,-1) and D(-1,-5) is a rectangle.

    I tried find AB dot BC = 0, but I'm not getting 0. So I'm stumped. Can someone help me out? =/
  2. jcsd
  3. Jul 28, 2006 #2


    User Avatar
    Science Advisor

    Just check your arithmetic.
  4. Jul 28, 2006 #3
    Try BA dot BC
  5. Jul 28, 2006 #4


    User Avatar
    Science Advisor

    You are aware, are you not, that AB= -BA so that if AB dot BC= 0, so is BA dot BC?

    Hollysmoke, could you show us what you got for AB and BC? I wondering if you were sufficiently careful of signs while subtracting.
  6. Jul 28, 2006 #5
    pfft, you are right. That's what I get for posting late at night. :rolleyes:
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook