document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=828965>Question 828965</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Find The value of cos2x if cotx=12/5, where pi < x <3pi/2 </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #499817 by </B><A HREF=/tutors/aboutme.mpl?userid=lwsshak3><B>lwsshak3(11628)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=lwsshak3><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=499817\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Find The value of cos2x if cotx=12/5, where pi < x <3pi/2<BR>\n" );
document.write( "cotx=12/5(working with a (5-12-13) reference right triangle in quadrant III in which sin<0, cos<0<BR>\n" );
document.write( "sinx=-5/13<BR>\n" );
document.write( "cosx=-12/13<BR>\n" );
document.write( "..<BR>\n" );
document.write( "cos2x=cos^2x-sin^2x=144/169-25/169=119/169<BR>\n" );
document.write( "..<BR>\n" );
document.write( "Calculator check:<BR>\n" );
document.write( "cosx=-12/13 in quadrant III<BR>\n" );
document.write( "x&#8776;202.62<BR>\n" );
document.write( "2x&#8776;405.24&#730;<BR>\n" );
document.write( "cos2x&#8776;cos(405.24)&#8776;0.7041..<BR>\n" );
document.write( "Exact value as calculated=119/169&#8776;0.7041.. </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );