document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=690368>Question 690368</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Please help me solve this equation<BR>\n" );
document.write( "use a double angle formulas to find the exact value of cos2u when sinu=3/5, where pi/2<u<pi </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #426287 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=426287\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> use a double angle formulas to find the exact value of cos2u when sinu=3/5, where pi/2<u<pi<BR>\n" );
document.write( "..<BR>\n" );
document.write( "cos2u=1-2sin^u<BR>\n" );
document.write( "=1-2*(3/5)^2<BR>\n" );
document.write( "=1-18/25<BR>\n" );
document.write( "=7/25<BR>\n" );
document.write( "..<BR>\n" );
document.write( "calculator check:<BR>\n" );
document.write( "u=sin^-1(3/5)&#8776;2.498 (in quadrant II)<BR>\n" );
document.write( "2u&#8776;4.9961 (in quadrant IV where cos>0)<BR>\n" );
document.write( "cos2u=cos(4.9961)&#8776;0.2799..<BR>\n" );
document.write( "7/25=0.28 </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );