Results 1 to 4 of 4

Math Help - Finding the area of a triangle using vector projections.

  1. #1
    Newbie
    Joined
    Jan 2011
    Posts
    3

    Finding the area of a triangle using vector projections.

    Wasn't for sure if this should be posted here or in the Linear Algebra forum. It's in my Linear Algebra class but is still fairly basic stuff I think..

    I can't seem to get the correct answer for question 47 from this page and can't figure out what I am doing wrong. I tried using the formula given and also tried using the basic 1/2bh (which gives the same formula):
    Finding the area of a triangle using vector projections.-math001n.jpg
    Here's my work (a bit all over the place but should be readable, any questions ask.)
    Finding the area of a triangle using vector projections.-math002.jpg

    My final answer would have been 1/2sqr(6)sqr(11/2) but simplified or whatever. The answer in the back is 1/2sqr(45) though and I can't seem to find my mistake.

    Thanks in advance guys (or girls.)
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Newbie
    Joined
    Jan 2011
    Posts
    3
    Found a mistake in my work. The Projection of AC onto AB should actually be -1/3 in the z frame not 1/3. However I am still getting the wrong final answer. Allowing that to substitue changes the norm of AB subtract the projection to be 7/3. Still gives me the wrong answer of 7/6sqr(6)
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Jan 2011
    Posts
    3
    Nevermind on that last post my math is all over the map but I still can't seem to find the answer.
    1/2sqr(49) is the latest/closest answer yet. still looking for little mistakes.
    Follow Math Help Forum on Facebook and Google+

  4. #4
    MHF Contributor
    Joined
    Mar 2010
    From
    Florida
    Posts
    3,093
    Thanks
    5
    Quote Originally Posted by Cheesehunk View Post
    Nevermind on that last post my math is all over the map but I still can't seem to find the answer.
    1/2sqr(49) is the latest/closest answer yet. still looking for little mistakes.
    Can you type up your work?

    It is hard to read off the paper.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Finding area of 3D triangle
    Posted in the Calculus Forum
    Replies: 2
    Last Post: September 13th 2010, 11:27 AM
  2. Replies: 4
    Last Post: August 6th 2010, 10:25 PM
  3. Area of triangle using vector products.
    Posted in the Pre-Calculus Forum
    Replies: 1
    Last Post: May 26th 2010, 10:21 AM
  4. Replies: 2
    Last Post: February 24th 2009, 10:32 AM
  5. Replies: 3
    Last Post: January 27th 2009, 12:53 PM

Search Tags


/mathhelpforum @mathhelpforum