Question 550468
<pre>
Given: &#5123;ABC, 
       AB &#8773; AC, 
       AD bisects &#8736;BAC 

To prove: AD &#8869; BC 
 
{{{drawing(300,300,-1.5,1.5,-.5,4.5, triangle(-1,0,1,0,0,4),
locate(-1,0,B), locate(1,0,C), locate(0,4.2,A), green(line(0,0,0,4)),
locate(0,0,D) )}}} 

 Steps:                       Reasons:
1.   AB &#8773; AC                  Why?
2. &#8736;ABD &#8773; &#8736;ACD               Why?
3.   AD &#8773; AD                  Why?
4. &#5123;ABD &#8773; &#5123;ADC               Why?
5. &#8736;ADB &#8773; &#8736;ACD               Why? 
6.  m&#8736;ADB = m&#8736;ACD = 90°      Two congruent angles that form a linear 
                              pair are right angles

7.   AD &#8869; AC                  Why?              
8.   AD is an altitude        Why?

I filled in the reason for step 6.  You fill in the reasons for the
other steps.  You could combine two of the steps.

Edwin</pre>