Results 1 to 4 of 4
Like Tree2Thanks
  • 1 Post By Plato
  • 1 Post By HallsofIvy

Math Help - Exterior angles

  1. #1
    Member
    Joined
    Aug 2012
    From
    Utah
    Posts
    88

    Exterior angles

    In the diagram(please see attachment), the exterior angles of triangle ABC are <FAC, <ACD, <ECB, <CBI, <HBA and <BAG. What about the angles <, <DCE, <HBI, are they not exterior?
    Attached Thumbnails Attached Thumbnails Exterior angles-exterior-angles.png  
    Last edited by hisajesh; July 16th 2013 at 02:57 PM.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor

    Joined
    Aug 2006
    Posts
    18,605
    Thanks
    1574
    Awards
    1

    Re: Exterior angles

    Quote Originally Posted by hisajesh View Post
    In the diagram(please see attachment), the exterior angles of triangle ABC are <FAC, <ACD, <ECB, <CBI, <HBA and <BAG. What about the angles <, <DCE, <HBI, are they not exterior?
    Look at this webpage.

    Note that \angle GAB has a side of \Delta ABC, \overline{AB}, as a subset.

    But \angle GAH has no side of \Delta ABC, as a subset.
    Last edited by Plato; July 16th 2013 at 03:29 PM.
    Thanks from hisajesh
    Follow Math Help Forum on Facebook and Google+

  3. #3
    MHF Contributor

    Joined
    Apr 2005
    Posts
    15,368
    Thanks
    1313

    Re: Exterior angles

    The definition of "exterior angle". is "

    Exterior Angles of Polygons
    "The Exterior Angle is the angle between any side of a shape,
    and a line extended from the next side."

    http://en.wikipedia.org/wiki/Internal_and_external
    "an exterior angle (or external angle) is an angle formed by one side of a simple, closed polygon and a line extended from an adjacent side."

    What you have is two "lines extended from adjacent sides".
    Last edited by HallsofIvy; July 16th 2013 at 03:32 PM.
    Thanks from hisajesh
    Follow Math Help Forum on Facebook and Google+

  4. #4
    MHF Contributor

    Joined
    Aug 2006
    Posts
    18,605
    Thanks
    1574
    Awards
    1

    Re: Exterior angles

    This strictly a post script to both of the replies posted.

    I have no idea what level we are actually dealing with.
    I would like to nail a definition for an exterior angle of a convex polygon.

    This is due to R.L.Moore by way of his student Ed Moise in ELEMENTRY GEOMETY: from an advanced standpoint.
    We need to know what it means that two angles form a linear pair.

    We say that \angle XAB is an exterior angle if and only if that angle forms a linear pair with an interior of the polygon with vertex A
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. [SOLVED] Exterior circle angles, how to calculate?
    Posted in the Geometry Forum
    Replies: 3
    Last Post: July 19th 2011, 08:02 AM
  2. exterior algebra in R3
    Posted in the Differential Geometry Forum
    Replies: 3
    Last Post: November 7th 2010, 01:55 AM
  3. Interior and Exterior Angles of Polygons
    Posted in the Geometry Forum
    Replies: 5
    Last Post: March 1st 2010, 04:58 PM
  4. Exterior angles of a convex polygon HELP?
    Posted in the Geometry Forum
    Replies: 3
    Last Post: September 3rd 2009, 03:21 AM
  5. Exterior and Interior Angles
    Posted in the Geometry Forum
    Replies: 1
    Last Post: December 20th 2007, 10:00 PM

Search Tags


/mathhelpforum @mathhelpforum