document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=596221>Question 596221</A>: <I><SPAN STYLE=\"word-break: break-all;\"> verify the question algebraically \r<BR>\n" );
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document.write( "cos(x-y)+cos(x+y)=2cosxcosy </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #377602 by </B><A HREF=/tutors/aboutme.mpl?userid=jim_thompson5910><B>jim_thompson5910(35256)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=jim_thompson5910><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=377602\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> cos(x-y)+cos(x+y)=2cos(x)cos(y)\r<BR>\n" );
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document.write( "[cos(x)cos(y)+sin(x)sin(y)]+[cos(x)cos(y)-sin(x)sin(y)]=2cos(x)cos(y)\r<BR>\n" );
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document.write( "cos(x)cos(y)+sin(x)sin(y)+cos(x)cos(y)-sin(x)sin(y)=2cos(x)cos(y)\r<BR>\n" );
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document.write( "[cos(x)cos(y)+cos(x)cos(y)]+[sin(x)sin(y)-sin(x)sin(y)]=2cos(x)cos(y)\r<BR>\n" );
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document.write( "2cos(x)cos(y)=2cos(x)cos(y)\r<BR>\n" );
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document.write( "This verifies the identity. </SPAN>\n" );
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