document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=388770>Question 388770</A>: <I><SPAN STYLE=\"word-break: break-all;\"> How to write a 2 column proof to show that an angle bisector of the vertex of an isosceles triangle is also an altitude. </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #275382 by </B><A HREF=/tutors/aboutme.mpl?userid=richard1234><B>richard1234(7193)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=richard1234><IMG SRC=http://www.algebra.com/images/aboutme-small.gif BORDER=0 alt=\"About Me\" VALIGN=MIDDLE></A>&nbsp;<IMG SRC=http://www.algebra.com/cgi-bin/show-face.mpl?user=richard1234><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=275382\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> I'm not very experienced with writing two-column proofs on this site, or drawing diagrams on this site but I'll give you an outline:\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "Let the triangle be ABC with angle A = angle C, and BD be the altitude. Since BD is an altitude, then angle ADB = angle CDB = 90 degrees, and since angle A = angle C, angle ABD = angle CBD. By SAS, triangles ABD and CBD are congruent, and then you can show that the altitude is also an angle bisector. </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );