document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=626368>Question 626368</A>: <I><SPAN STYLE=\"word-break: break-all;\"> how to verify:<BR>\n" );
document.write( "tan^4 x + 2 tan^2 x + 1 = sec^4 x </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #394144 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=394144\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> how to verify:<BR>\n" );
document.write( "tan^4 x + 2 tan^2 x + 1 = sec^4 x<BR>\n" );
document.write( "**<BR>\n" );
document.write( "start with left side:<BR>\n" );
document.write( "tan^4x+2tan^2x+1=(tan^2x+1)^2<BR>\n" );
document.write( "identity:tan^2x=sec^2x-1<BR>\n" );
document.write( "(tan^2x+1)^2<BR>\n" );
document.write( "=(sec^2x-1+1)^2<BR>\n" );
document.write( "=sec^4x<BR>\n" );
document.write( "verified: left side=right side </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );