document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=872899>Question 872899</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Find the exact value for cos2x given sinx= square root5/5<BR>\n" );
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document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #526502 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=526502\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Find the exact value for cos(2x) given sin(x) = sqrt(5)/5<BR>\n" );
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document.write( "cos(2x) = sin^2-cos^2 = sin^2-(1-sin^2) = 2sin^2(x)-1<BR>\n" );
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document.write( "Your Problem:<BR>\n" );
document.write( "cos(2x) = 2(sqrt(5)/5)^2 -1 = 2(1/5) - 1 = -3/5<BR>\n" );
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document.write( "Cheers,<BR>\n" );
document.write( "Stan H.<BR>\n" );
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