How do we use properties of trapezoids?

12.7.12

First thing to know is what is a trapezoid.

• A trapezoid has exactly one pair of parallel lines

 

Properties of trapezoids

1. Trapezoid Consecutive Angles Conjecture                                                                                         -The consecutive angles between the bases of a trapezoid are 180 degrees (supplementary).

     2. Isosceles Trapezoid Conjecture 

         - The base angles of an isosceles trapezoid are congruent.

<A is congruent to <D.

Try solving this:  Find x.

  

1st step: 2x+5=3x+2

2nd step:subtract 2x from both sides

                                                    Equation should look like this: 5=x+2

3rd step: subtract 2 from both sides and you get your answer.

                                                    Answer is 3+x

* You don't do this to 4x-2 and 5x+3 because those are parallel not congruent.

1st picture from http://www.google.com/imgresum=1&hl=en&tbo=d&biw=1517&bih=693&tbm=isch&tbnid=sGz7fgFw41GoMM:&imgrefurl=http://www.ck12.org/concept/Trapezoids---Intermediate/&docid=eeMQ8dVhvkcDNM&imgurl=http://www.ck12.org/flx/show/image/user%25253Ack12editor/201209241348511282764513_dff7a8f97ef56047035788567c45fc33-201209241348512460267699.png&w=708&h=511&ei=MabCUMukGPC10AGlqYG4Aw&zoom=1&iact=hc&vpx=4&vpy=274&dur=292&hovh=191&hovw=264&tx=128&ty=97&sig=108818101793549926599&page=2&tbnh=145&tbnw=202&start=27&ndsp=38&ved=1t:429,r:42,s:0,i:215

2nd picture from http://www.geom.uiuc.edu/~dwiggins/conj22.html

  

WHAT ARE THE RHOMBUS'S CONJECTURES?