document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=41213>Question 41213</A>: <I><SPAN STYLE=\"word-break: break-all;\"> how many diagonals are in a 21-gon? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #26612 by </B><A HREF=/tutors/aboutme.mpl?userid=Nate><B>Nate(3500)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Nate><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=26612\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> If diagonals are the lines that connect minus the sides to make the 21-gon:<BR>\n" );
document.write( "I have thought about polygons like these, and my idea can make this easy:<BR>\n" );
document.write( "(1) + (2) + (3) + .... for (s - 1) amount of times where <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=s ALIGN=MIDDLE  ALT=\"s\"   DISABLED_style= \"max-width:90%; height:auto;\" > is the number of sides<BR>\n" );
document.write( "1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 ....<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=SUM+=+%28n%2F2%29%28a1+%2B+an%29 ALIGN=MIDDLE  ALT=\"SUM+=+%28n%2F2%29%28a1+%2B+an%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=SUM+=+%2820%2F2%29%281+%2B+20%29 ALIGN=MIDDLE  ALT=\"SUM+=+%2820%2F2%29%281+%2B+20%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=SUM+=+%2810%29%2821%29 ALIGN=MIDDLE  ALT=\"SUM+=+%2810%29%2821%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=SUM+=+210 ALIGN=MIDDLE  ALT=\"SUM+=+210\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "minus the sides that connect:<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=210+-+21+=+x ALIGN=MIDDLE  ALT=\"210+-+21+=+x\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=189+=+x ALIGN=MIDDLE  ALT=\"189+=+x\"   DISABLED_style= \"max-width:90%; height:auto;\" > </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );