document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=971855>Question 971855</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Hello Tutor, I really need your help to answer this question please. \r<BR>\n" );
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document.write( "3. Verify the following identity by using an angle sum identity: cos (2x)  = 1 – 2(sin2 x).  Hint (2x = x + x) </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #594240 by </B><A HREF=/tutors/aboutme.mpl?userid=Boreal><B>Boreal(15235)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Boreal><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=Boreal><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=594240\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> double angle identity for cos (x+y)\r<BR>\n" );
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document.write( "=cosx*cosy - sinx*siny\r<BR>\n" );
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document.write( "=cosx^2 - sinx^2  since y=x\r<BR>\n" );
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document.write( "But cos^2 x + sin^2 x =1\r<BR>\n" );
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document.write( "Therefore, cos (2x)= 1-sin^2 x -sin^2 x substituting in two lines above.\r<BR>\n" );
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document.write( "cos (2x)=1-2 sin^2 x </SPAN>\n" );
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