document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=635024>Question 635024</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Hello,<BR>\n" );
document.write( "The problem that I have is that I need to verify the identity:<BR>\n" );
document.write( "         sin^4x+cos^4x=1-2cos^2x+2cos^4x<BR>\n" );
document.write( "I started with the right hand side and I tried to group the two cosine identities<BR>\n" );
document.write( "=1-2cos^2x+2cos^4x<BR>\n" );
document.write( "=1-2cos^2x(1-cos^2x)<BR>\n" );
document.write( "using the Pythagorean identity I got<BR>\n" );
document.write( "=1-2cos^2x(sin^2x)<BR>\n" );
document.write( "I'm not sure if I can use the Pythagorean identity on the first part making it<BR>\n" );
document.write( "=(2sin^2x)(sin^2x)<BR>\n" );
document.write( "But if I do, I'm not getting any closer to the left hand side. <BR>\n" );
document.write( "Please help, or tell me if I'm at least on the right track.<BR>\n" );
document.write( "Thank you  </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #400051 by </B><A HREF=/tutors/aboutme.mpl?userid=richwmiller><B>richwmiller(17219)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=richwmiller><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=richwmiller><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=400051\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> You have cos^4x on both sides.<BR>\n" );
document.write( "so subtracting it from both sides<BR>\n" );
document.write( "sin^4x=1-2cos^2x+cos^4x<BR>\n" );
document.write( "apparently this is a known identity.<BR>\n" );
document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );