document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=3904>Question 3904</A>: <I><SPAN STYLE=\"word-break: break-all;\"> area of a regular pentagon inscribed in a circle of radius 12cm.        </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #1716 by </B><A HREF=/tutors/aboutme.mpl?userid=khwang><B>khwang(438)</B></A><img src=\"/images/stars/stars-10.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=khwang><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=1716\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\">  Let AB be a side of the pentagon and O be the center.\r<BR>\n" );
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document.write( "  then angle AOB = 360/5 = 72 degrees.<BR>\n" );
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document.write( " And the area of AOB = 1/2 AOsin angle AOB<BR>\n" );
document.write( "                     = 1/2 r^2 sin AOB = 1/2 * 144 sin 72'<BR>\n" );
document.write( "                     = 72 sin 72 = 68.48 cm^2\r<BR>\n" );
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document.write( " So the area of the pentagon = 5 area of triangle AOB = 342.38 cm^2\r<BR>\n" );
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document.write( " Kenny </SPAN>\n" );
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