document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=391000>Question 391000</A>: <I><SPAN STYLE=\"word-break: break-all;\"> I have a circle inside a regular pentagon. CE is from top of pentagon to the bottom.  I know that CE is 1.4375. I need to find DE which is the radius of the circle. CE is a straight line going all the way through middle of the circle. </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #277312 by </B><A HREF=/tutors/aboutme.mpl?userid=scott8148><B>scott8148(6628)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=scott8148><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=scott8148><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=277312\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> picture the pentagon divided into ten congruent right triangles<BR>\n" );
document.write( "___ by lines drawn from the midpoint of a side to the opposite vertex\r<BR>\n" );
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document.write( "the \"central\" angle of the right triangle (in the center of the pentagon) is 36º (360º / 10)\r<BR>\n" );
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document.write( "the length of the side of the triangle from the right angle to the center of the pentagon is D/2<BR>\n" );
document.write( "___ this same side , added to the hypotenuse of the right triangle , equals C\r<BR>\n" );
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document.write( "(D / 2) + h = C\r<BR>\n" );
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document.write( "from trigonometry ___ (D / 2) / h = cos(36º) ___ (D / 2) / cos(36º) = h\r<BR>\n" );
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document.write( "substituting ___ (D / 2) + [(D / 2) / cos(36º)] = C\r<BR>\n" );
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document.write( "D{1 + [1 / cos(36º)]} = 2C\r<BR>\n" );
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document.write( "D = 2C / {1 + [1 / cos(36º)]} </SPAN>\n" );
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