Results 1 to 5 of 5

Math Help - Help with simple geometry :D

  1. #1
    Newbie
    Joined
    Feb 2011
    Posts
    4

    Post Help with simple geometry :D

    Hello, I'm new to math help forums. I hope you could help me.

    I have a test tomorrow and I'm having trouble with a certain subject. I don't know what it's called in English, but it's those triangles that have at least one 90 degrees angle in them. It's pretty simple. Just basic triangle rules. But the tests are very tricky and I got this work that's supposed to prepare me but I can't solve anything! If you could help me it would make it a lot easier for me to figure out how to solve such problems in the future. Ok, so, here we go.

    There's this triangle
    Help with simple geometry :D-2rdb7r8.png

    Here's the info(I'm from Israel so forgive me if I don't hit all the terms :P)

    Triangle ABC is a right triangle(AB perpendicular to BC)
    BD is the midpoint of AC
    AE = CE
    AE perpendicular to BD

    Calculate the angle C

    I don't really know how to use the MATH tags so sorry if it looks a little bad. I tried solving it, but I can't figure out how I'm supposed to get angles here if the only angle I know it's size is B which is 90?

    Thanks for your help
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Super Member
    earboth's Avatar
    Joined
    Jan 2006
    From
    Germany
    Posts
    5,830
    Thanks
    123
    Quote Originally Posted by thejack View Post
    Hello, I'm new to math help forums. I hope you could help me.

    ...
    There's this triangle

    Here's the info

    Triangle ABC is a right triangle(AB perpendicular to BC)
    BD is the midpoint of AC
    AE = CE
    AE perpendicular to BD

    Calculate the angle C

    I don't really know how to use the MATH tags so sorry if it looks a little bad. I tried solving it, but I can't figure out how I'm supposed to get angles here if the only angle I know it's size is B which is 90? <== that's wrong. See the highlighted part of the question.

    Thanks for your help
    1. I've modified your sketch a little bit (see attachment).

    2. Since |\overline{AE}|=|\overline{CE}| the triangle ACE is isosceles. Let x denote the value of the angle at C then the exterior angle of the triangle at E must have the value 2x.

    3. Since |\overline{BC}| = |\overline{BD}| = |\overline{BA}| (circle of Thales!) the triangle CBD is isosceles. Therefore the angle \angle(DBC) has a value of x.

    4. Take the greyed triangle. The sum of all interior angles of this triangle is:

    2x+x+90^\circ=180^\circ

    Solve for x.
    Attached Thumbnails Attached Thumbnails Help with simple geometry :D-winklrw3eck.png  
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Feb 2011
    Posts
    4
    Quote Originally Posted by earboth View Post
    1. I've modified your sketch a little bit (see attachment).

    2. Since |\overline{AE}|=|\overline{CE}| the triangle ACE is isosceles. Let x denote the value of the angle at C then the exterior angle of the triangle at E must have the value 2x.

    3. Since |\overline{BC}| = |\overline{BD}| = |\overline{BA}| (circle of Thales!) the triangle CBD is isosceles. Therefore the angle \angle(DBC) has a value of x.

    4. Take the greyed triangle. The sum of all interior angles of this triangle is:

    2x+x+90^\circ=180^\circ

    Solve for x.
    thanks
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Super Member
    Joined
    Nov 2007
    From
    Trumbull Ct
    Posts
    918
    Thanks
    27
    Hello earboth.
    I Think your statement 3 needs correction


    bjh
    Follow Math Help Forum on Facebook and Google+

  5. #5
    MHF Contributor
    Joined
    Dec 2009
    Posts
    3,120
    Thanks
    1
    Just a typo by Earboth.

    He meant |\overline{DC}|=|\overline{DA}|=|\overline{DB}|
    Attached Thumbnails Attached Thumbnails Help with simple geometry :D-thales.jpg  
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Simple geometry
    Posted in the Geometry Forum
    Replies: 3
    Last Post: January 25th 2009, 03:11 PM
  2. simple geometry..
    Posted in the Math Topics Forum
    Replies: 2
    Last Post: October 29th 2008, 09:41 AM
  3. Simple Geometry
    Posted in the Geometry Forum
    Replies: 3
    Last Post: June 1st 2008, 10:42 AM
  4. Simple Geometry
    Posted in the Geometry Forum
    Replies: 2
    Last Post: May 29th 2008, 03:05 AM
  5. Simple Coordinate geometry...
    Posted in the Pre-Calculus Forum
    Replies: 2
    Last Post: March 10th 2008, 02:19 PM

/mathhelpforum @mathhelpforum