document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=766927>Question 766927</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Find the exact value given that sin A = -4/5 with A in quadrant IV, tan B= 7/24 with B in quadrant III, and cos C= -5/13 with C in quadrant II\r<BR>\n" );
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document.write( "Cos 2A </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #467330 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=467330\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Find the exact value given that sin A = -4/5 with A in quadrant IV<BR>\n" );
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document.write( "Since sin = y/4, y = -4 and r = 5<BR>\n" );
document.write( "Then x = sqrt[5^2-4^2] = sqrt[9] = 3<BR>\n" );
document.write( "So cos(A) = 3/5<BR>\n" );
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document.write( "Cos 2A = cos^2(A)-sin^2(A) = (3/5)^2 - (4/5)^2 = -7/25<BR>\n" );
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document.write( "Cheers,<BR>\n" );
document.write( "Stan H.<BR>\n" );
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