document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=703820>Question 703820</A>: <I><SPAN STYLE=\"word-break: break-all;\"> esatblish each idenntity\r<BR>\n" );
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document.write( " cot theta - tan theta over cot theta + tan theta = cos 2theta </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #433753 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=433753\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> cot theta - tan theta over cot theta + tan theta = cos 2theta<BR>\n" );
document.write( "use x for theta<BR>\n" );
document.write( "(cotx-tanx)/(cotx+tanx)=cos2x<BR>\n" );
document.write( "start with left side:<BR>\n" );
document.write( "(cotx-tanx)/(cotx+tanx)<BR>\n" );
document.write( "=[(cosx/sinx)-(sinx/cosx)]/[(cosx/sinx)+(sinx/cosx)]<BR>\n" );
document.write( "=[(cos^2x-sin^2x)/(sinxcosx)]/[(cos^2x+sin^2x)/(sinxcosx)]<BR>\n" );
document.write( "sinxcosx cancels out, (cos^2x+sin^2x)=1<BR>\n" );
document.write( "=(cos^2x-sin^2x)<BR>\n" );
document.write( "=cos2x<BR>\n" );
document.write( "verified: left side=right side </SPAN>\n" );
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