document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=257494>Question 257494</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Given: Triangle ABC\r<BR>\n" );
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document.write( "Prove: m<4= m<1 + m<2\r<BR>\n" );
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document.write( "Picture: A triangle with line, CD, connected to it. A is m<1, B is m<2, C is m<3, and m<4 are vertical angles to m<3 </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #189420 by </B><A HREF=/tutors/aboutme.mpl?userid=drk><B>drk(1908)</B></A><img src=\"/images/stars/stars-12.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=drk><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/images/nopicture.jpg><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=189420\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> This is also called the exterior triangle theorem. With angle 4 vertical to angle 3, you cannot prove <BR>\n" );
document.write( "angle 4 = angle 1 + angle 2. For this to work, angle 4 must be supplementary to angle 3. Here is the proof for that.<BR>\n" );
document.write( "STATEMENT 1: triangle ABC <BR>\n" );
document.write( "REASON 1: given<BR>\n" );
document.write( "STATEMENT 2: angle 1 + angle 2 + angle 3 = 180 degrees<BR>\n" );
document.write( "REASON 2: definition of sum of angles of  triangle <BR>\n" );
document.write( "STATEMENT 3: angle 3 + angle 4 = 180<BR>\n" );
document.write( "REASON 3: definition of supplementary angles <BR>\n" );
document.write( "STATEMENT 4: angle 1 + angle 2 + angle 3 = angle 3 + angle 4<BR>\n" );
document.write( "REASON 4: substitution [2,3]<BR>\n" );
document.write( "STATEMENT 5: angle 1 + angle 2 = angle 4<BR>\n" );
document.write( "REASON 5: subtraction property of equality </SPAN>\n" );
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