document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=434491>Question 434491</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Verify The Equation is an Identity<BR>\n" );
document.write( "cosx*cos(-x)-sinx*sin(-x)=1<BR>\n" );
document.write( "how do I do it??? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #301214 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=301214\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Verify The Equation is an Identity<BR>\n" );
document.write( "cosx*cos(-x)-sinx*sin(-x)=1<BR>\n" );
document.write( ".. <BR>\n" );
document.write( "cos(-x)=cos(x)  (cos is an even function)<BR>\n" );
document.write( "sin (-x)=-sinx   (sin is an odd function)<BR>\n" );
document.write( "..<BR>\n" );
document.write( "cosx*cos(-x)-sinx*sin(-x)<BR>\n" );
document.write( "cosx*cosx-(sinx*(-sinx)=cos^2x+sin^2x=1 </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );