document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1104639>Question 1104639</A>: <I><SPAN STYLE=\"word-break: break-all;\"> In triangle ABC, BC is the greatest side then, prove that Angle A is greater than 2/3 of the right angle.  </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #719347 by </B><A HREF=/tutors/aboutme.mpl?userid=greenestamps><B>greenestamps(13200)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=greenestamps><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=greenestamps><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=719347\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> <br><BR>\n" );
document.write( "Do you need some sort of formal proof?<br><BR>\n" );
document.write( "The statement is rather obvious.<br><BR>\n" );
document.write( "\"2/3 of a right angle\" means 60 degrees.<BR>\n" );
document.write( "An equilateral triangle has all angles 60 degrees.<BR>\n" );
document.write( "If a triangle is not equilateral, then at least one of its angles is greater than 60 degrees.<BR>\n" );
document.write( "If BC is the longest side, then the triangle is not equilateral.<BR>\n" );
document.write( "The largest angle is opposite the longest side.<BR>\n" );
document.write( "Angle A is opposite side BC.<br><BR>\n" );
document.write( "Therefore, if BC is the longest side, then angle A is greater than 60 degrees.<BR>\n" );
document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );