Page 2 of 2 FirstFirst 12
Results 16 to 20 of 20

Math Help - Angle bisection problem, with very few measures

  1. #16
    Member
    Joined
    Mar 2011
    Posts
    99

    Thumbs up Re: Angle bisection problem, with very few measures

    Quote Originally Posted by bjhopper View Post
    Hi Zellator,
    If I understand your new post you want to know how to find the lengths of AB and AC using Stewards Theorem. I am not familar with it but I have a plan for you.
    Draw a vertical line length 6 Mark upper end A and lower D.At point D swing two arcs lengths of 3 and 4.A straight line thru D defines two points B and C.Note that you can draw many triangles.If you fix the length of either AB or AC the other line can be calculated using the cosine law
    Hi bjhopper! Thanks again for your reply

    I understand most of your explanation but I didn't understand some parts, where you said to swing arcs and a vertical line.
    If you ever wish to make some quick graphs, not only on this thread. There's a tool called CaRMetal that is by java, so you don't have to install anything.
    So we can better understand you. Search CaRMetal on Google, it is a French program



    What do you mean with many triangles?
    And what do you mean with fixing the length?

    Here's what I got
    9=36+x^2-12xcos{(a)}
    cos{(a)}=\frac{+x^2+25}{12x}
    and
    16=36+y^2-12ycos{(a)}
    cos{(a)}=\frac{+y^2+20}{12y}

    If we were to equal those two equations, would we get anywhere?

    About the Stewart's Theorem,
    the theorem is a(mn+d^2)=b^2m+c^2n
    But we can't use it here with that few measures.
    But I didn't want to do it with it,

    The last time I did this question, I didn't get it right. That's why I am asking for it again.
    I used a property of right triangles, and we don't know if this is a right triangle (eventually we do, but).
    I don't know how you guys got AC=6 with the bisector theorem

    If I get something wrong, it is maybe because it is late here and I am kind of tired hahaha
    Thanks bjhopper!
    Follow Math Help Forum on Facebook and Google+

  2. #17
    Super Member
    Joined
    Nov 2007
    From
    Trumbull Ct
    Posts
    917
    Thanks
    27

    Re: Angle bisection problem, with very few measures

    Hi Zellator,
    No one calculated AD you supplied it.In order to calculate one of the other sides requires a length of one of them.Given 5 for AC you can find AB using the cosine law .Try it your way. (Stewards Theorem)The angle bisector theorem does not enter the problem because the angles at A will not be equal



    bjh
    Follow Math Help Forum on Facebook and Google+

  3. #18
    Member
    Joined
    Mar 2011
    Posts
    99

    Re: Angle bisection problem, with very few measures

    Why the angles will not be equal at A? Isn't this bisection?


    We know only CD BD and AD.
    If we have AC it is easy to calculate AB, but how do we calculate AC?
    I don't think you understood my question

    We are out of one length here to find the other
    We need b or c to calculate either by Cosine's Law or by Stewart's Theorem.

    By Stewart's Theorem we have
    8(12+6^2)=3b^2+4c^2

    And I did by Cosine's Law in my previous post.
    I still don't get it bjhopper.
    Thank you for having pacience with me hahahah
    Thanks.
    Follow Math Help Forum on Facebook and Google+

  4. #19
    Super Member
    Joined
    Nov 2007
    From
    Trumbull Ct
    Posts
    917
    Thanks
    27

    Re: Angle bisection problem, with very few measures

    Zellator,
    Given only AD BD BC then AC cannot be calculated.


    bjh
    Follow Math Help Forum on Facebook and Google+

  5. #20
    Member
    Joined
    Mar 2011
    Posts
    99

    Re: Angle bisection problem, with very few measures

    Quote Originally Posted by Zellator View Post
    In \Delta ABC, let D be a point in BC such that AD bisects angle A. Given that AD=6, BD=4, and DC=3, find AB.
    This is what the problem stated, then how is it possible to solve it?
    Follow Math Help Forum on Facebook and Google+

Page 2 of 2 FirstFirst 12

Similar Math Help Forum Discussions

  1. Triangle angle measures
    Posted in the Geometry Forum
    Replies: 5
    Last Post: March 28th 2010, 01:42 PM
  2. Angle measures in radians & degrees
    Posted in the Pre-Calculus Forum
    Replies: 5
    Last Post: September 3rd 2009, 03:38 PM
  3. Bisection method problem
    Posted in the Calculus Forum
    Replies: 1
    Last Post: June 10th 2009, 03:30 PM
  4. Finding Angle measures
    Posted in the Geometry Forum
    Replies: 2
    Last Post: March 2nd 2009, 12:42 PM
  5. Angle measures
    Posted in the Geometry Forum
    Replies: 16
    Last Post: May 1st 2008, 12:59 PM

Search Tags


/mathhelpforum @mathhelpforum