document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=770143>Question 770143</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Solution for cos4x=cos2x<BR>\n" );
document.write( " </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #469322 by </B><A HREF=/tutors/aboutme.mpl?userid=Alan3354><B>Alan3354(69443)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Alan3354><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=Alan3354><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=469322\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Solution for cos4x=cos2x<BR>\n" );
document.write( "------------<BR>\n" );
document.write( "cos(2A) = 2cos^2(A) - 1 double angle formula<BR>\n" );
document.write( "---<BR>\n" );
document.write( "cos4x=cos2x<BR>\n" );
document.write( "2cos^2(2x) - 1 = cos(2x)<BR>\n" );
document.write( "2cos^2(2x) - cos(2x) - 1 = 0<BR>\n" );
document.write( "(2cos + 1)*(cos - 1) = 0<BR>\n" );
document.write( "cos(2x) = 1<BR>\n" );
document.write( "2x = 0 + 2n*pi, n = 0,1,2,3...<BR>\n" );
document.write( "x = 0 + n*pi, n = 0,1,2,3...<BR>\n" );
document.write( "-----------<BR>\n" );
document.write( "cos(2x) = -1/2<BR>\n" );
document.write( "2x = 2pi/3, 4pi/3 + 2n*pi, n = 0,1,2,3...<BR>\n" );
document.write( "x = pi/3, 2pi/3 + n*pi, n = 0,1,2,3...<BR>\n" );
document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );