Question 516939
<pre>
Given: m&#8736;1 = m&#8736;2

And points D,F, and E are colinear
       __   __  
Prove: AB &#8869; ED 

                                  {{{drawing(300,300,-1,1,-1,1, line(-1,1,1,-1), line(-1,-1,1,1),
circle(0,0,.015), circle(-.67,.67,.015), circle(-.67,-.67,.015), circle(.67,.67,.015), circle(.67,-.67,.015), locate(-.7,.7,D), locate(-.7,-.7,A),   
locate(.7,.7,B),   
locate(.7,-.7,E),locate(0,.3,1),locate(.25,0.05,2),
circle(0,0,.01), circle(-.67,.67,.01), circle(-.67,-.67,.01), circle(.67,.67,.01), circle(.67,-.67,.01) 


  )}}}   
  






m&#8736;1 = m&#8736;2                                    Given

&#8736;1 and &#8736;2 form a linear pair              D,F, and E are colinear
                                           and adjacent angles
                                           which form a straight
                                           line form a linear pair 

&#8736;1 is supplementary to &#8736;2                 If two angles form a linear pair,
                                           they are supplementary


m&#8736;1 + m&#8736;2 = 180°                          Supplementary angles have sum 180°

m&#8736;1 + m&#8736;1 = 180°                          A quantity may be substituted
                                           for its equal

   2(m&#8736;1) = 180°                          Definition of like terms 

      m&#8736;1 = 90°                           Halves of equal quantities are
                                           equal

  &#8736;1 is a right angle                      Definition of a right angle is one
                                           whose measure is 90°
    __   __
    AB &#8869; ED                               Definition of perpendicular
                                           lines. 

Edwin</pre>