document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=631915>Question 631915</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Find the area of trapezoid ABCD if the vertices are A(1,5), B(7,3),C(2,-4), and D(-7,-1) </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #397914 by </B><A HREF=/tutors/aboutme.mpl?userid=Alan3354><B>Alan3354(69443)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Alan3354><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=Alan3354><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=397914\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Find the area of trapezoid ABCD if the vertices are A(1,5), B(7,3),C(2,-4), and D(-7,-1)<BR>\n" );
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document.write( "Do these like this:<BR>\n" );
document.write( "+A +B +C +D +A<BR>\n" );
document.write( "+1 +7 +2 -7 +1<BR>\n" );
document.write( "+5 +3 -4 -1 +5<BR>\n" );
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document.write( "Add the diagonals starting at the upper left.<BR>\n" );
document.write( "= 1*3 + 7*-4 + 2*-1 + -7*5 = 3 - 28 - 2 - 35 = -62<BR>\n" );
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document.write( "Add the diagonals starting at the lower left.<BR>\n" );
document.write( "= 5*7 + 3*2 + -4*-7 + -1*1 = 35 + 6 + 28 - 1 = +68<BR>\n" );
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document.write( "Then, <BR>\n" );
document.write( "Area = 1/2 the absolute value of the difference<BR>\n" );
document.write( "Diff = 130<BR>\n" );
document.write( "Area = 65 sq units.<BR>\n" );
document.write( "===========================<BR>\n" );
document.write( "This works for all polygons, any number of sides.\r<BR>\n" );
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document.write( " </SPAN>\n" );
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