Results 1 to 3 of 3

Math Help - Finding the sides with equal angles

  1. #1
    Junior Member
    Joined
    Aug 2009
    Posts
    62

    Finding the sides with equal angles

    In the given figure BA is parallel to CD, \angle DAC =\angle ABC. AB = 10cm, BC= 9cm, AC=15cm. What is the length of AD?

    I tried solving with AB/BC = AD/AC. The answer turned out to be wrong because the solution in the book is given as,
    Since \triangle ABC is similar to \triangleCAD, therefore, AB/BC = AC/AD.

    I did not understand why they considered \triangleCAD instead \triangleDAC and AB/BC = AC/AD accordingly.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor

    Joined
    Aug 2006
    Posts
    18,792
    Thanks
    1687
    Awards
    1
    Quote Originally Posted by saberteeth View Post
    I did not understand why they considered \triangleCAD instead \triangleDAC and AB/BC = AC/AD accordingly.
    In all cases involving similarly or congruence, the order in which we list the vertices in all important.
    In this case it must be \Delta ABC \approx \Delta CAD because \angle ABC \cong \angle CAD\;\& \,\angle BAC \cong \angle ACD.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Junior Member
    Joined
    Aug 2009
    Posts
    62
    Quote Originally Posted by Plato View Post
    In all cases involving similarly or congruence, the order in which we list the vertices in all important.
    In this case it must be \Delta ABC \approx \Delta CAD because \angle ABC \cong \angle CAD\;\& \,\angle BAC \cong \angle ACD.
    Oh thanks, now i understand..
    Last edited by saberteeth; September 7th 2009 at 06:25 PM.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 4
    Last Post: August 6th 2010, 10:25 PM
  2. Three known sides need angles
    Posted in the Trigonometry Forum
    Replies: 3
    Last Post: April 9th 2010, 10:52 AM
  3. Replies: 1
    Last Post: March 10th 2009, 11:55 PM
  4. Finding a triangles angles from its area + 2 sides?
    Posted in the Trigonometry Forum
    Replies: 2
    Last Post: February 9th 2009, 02:45 PM
  5. Tetrahedron with 3 sides and 3 angles known
    Posted in the Geometry Forum
    Replies: 0
    Last Post: May 16th 2007, 11:54 AM

Search Tags


/mathhelpforum @mathhelpforum