document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=389008>Question 389008</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Three points have coordinates A(1,2) to B(9,0) and C(6,t). Calculate the value(s) of t if:<BR>\n" );
document.write( "a) Angle ABC = 90 degrees,<BR>\n" );
document.write( "b) AC is perpendicular to BC.  </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #275492 by </B><A HREF=/tutors/aboutme.mpl?userid=Jk22><B>Jk22(389)</B></A><img src=\"/images/stars/stars-10.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Jk22><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=Jk22><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=275492\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> a) ABC has a right angle in B if : BA.BC = 0 = (8,-2).(-3,t) = -24 - 2t = 0<BR>\n" );
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document.write( "2t = -24 => t = -12<BR>\n" );
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document.write( "b) AC = (5,t-2) BC = (-3, t) AC is perpendicular to BC is AC.BC = 0  <BR>\n" );
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document.write( "AC.BC = -15 + t^2 - 2t = 0 = t^2 -2t - 15 = (t-5)(t+3)<BR>\n" );
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document.write( "hence t = -3 or 5 </SPAN>\n" );
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