document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=730054>Question 730054</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Which is the value of cos 2theta if cos theta= 5/13 and 0 degrees< theta < 90 degrees? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #446454 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=446454\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Which is the value of cos(2theta) if cos theta= 5/13 and 0 degrees< theta < 90 degrees?\r<BR>\n" );
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document.write( "Theta is in QI where x,y,and r are positive.<BR>\n" );
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document.write( "cos(theta) = 5/13 implies that x = 5 and r = 13<BR>\n" );
document.write( "Therefore y = sqrt[13^2-5^2] = 12<BR>\n" );
document.write( "So sin(theta) = y/r = 12/13<BR>\n" );
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document.write( "cos(2theta) = cos^2(theta)-sin^2(theta) = (5/13)^2-(12/13)^2 = -0.7041<BR>\n" );
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document.write( "Cheers,<BR>\n" );
document.write( "Stan H.<BR>\n" );
document.write( "================= </SPAN>\n" );
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