document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=830821>Question 830821</A>: <I><SPAN STYLE=\"word-break: break-all;\"> What is the exact value of cos(2theta) if tan(theta)=-3/4 and theta is in quadrant IV? <BR>\n" );
document.write( "I don't even know how to start this problem. Please show work, thanks </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #500909 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=500909\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> What is the exact value of cos(2theta) if tan(theta)=-3/4 and theta is in quadrant IV? <BR>\n" );
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document.write( "In QIV x is positive, y is negative and r is always positive in all quadrants.<BR>\n" );
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document.write( "tan = y/x so y = -3 and x = 4<BR>\n" );
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document.write( "Then  r = sqrt(3^2+4^2] = 5<BR>\n" );
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document.write( "sin = y/r = -3/5<BR>\n" );
document.write( "cos = x/r = 4/5<BR>\n" );
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document.write( "cos(2t) = cos^2(t)-sin^2(t) = (4/5)^2-(3/5)^2 = 7/25<BR>\n" );
document.write( "=================<BR>\n" );
document.write( "Cheers,<BR>\n" );
document.write( "Stan H.<BR>\n" );
document.write( "================= </SPAN>\n" );
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