document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1107546>Question 1107546</A>: <I><SPAN STYLE=\"word-break: break-all;\"> How to Verify this identity\r<BR>\n" );
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document.write( "cos(x+y)+cos(x-y)=2 cos x cos y </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #722556 by </B><A HREF=/tutors/aboutme.mpl?userid=stanbon><B>stanbon(75887)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=stanbon><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=722556\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Verify this identity <BR>\n" );
document.write( "cos(x+y)+cos(x-y)=2 cos x cos y <BR>\n" );
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document.write( "[cosx*cosy-sinx*siny] + [cosx*cosy + sinx*siny]<BR>\n" );
document.write( "-----<BR>\n" );
document.write( "= 2cos(x)cos(y)<BR>\n" );
document.write( "----<BR>\n" );
document.write( "Cheers,<BR>\n" );
document.write( "Stan H.<BR>\n" );
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document.write( " </SPAN>\n" );
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