1. Not finding help here? Sign up for a free 30min 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!

Vector Proofs

  1. Jan 21, 2008 #1
    1. The problem statement, all variables and given/known data
    I don't know if I'm posting in the right area, but here is the question:
    From the inequality: la dot bl= lal lbl lcos(theta)l is less than or equal to lal lbl

    Deduce the triangle inequality:
    la + bl is less than or equal to lal +lbl


    2. Relevant equations



    3. The attempt at a solution

    I am not even sure where to begin :(
    I'm wondering if I could use numbers to prove it, but that doesn't seem right.
     
  2. jcsd
  3. Jan 21, 2008 #2
    Sorry, misread. Think about (|a| + |b|)^2. You also have a property available to you that says |a|^2 = a dot a.
     
    Last edited: Jan 21, 2008
  4. Jan 21, 2008 #3
    |a+b|^2 =(a+b)dot(a+b) is a very nice identity application.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Vector Proofs
  1. Vector Proof (Replies: 1)

  2. Vector Proof (Replies: 2)

  3. Vector Proof (Replies: 0)

  4. Vector Proof (Replies: 2)

  5. Vector Proof (Replies: 11)

Loading...