document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=602898>Question 602898</A>: <I><SPAN STYLE=\"word-break: break-all;\"> If tan A = 9/40, A is in the first quadrant, cos B = -4/5, B is in the third quadrant, find the value of cos(A+B)\r<BR>\n" );
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document.write( "Please help me solve this problem. It's from the homework given to us today, which I have no chance of understanding since I missed class per the doctor's orders, and my friend's notes aren't really that readable...<BR>\n" );
document.write( "If you can, please show me the steps as well. It would really help me understand this lesson. Thank you! </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #380486 by </B><A HREF=/tutors/aboutme.mpl?userid=scott8148><B>scott8148(6628)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=scott8148><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=scott8148><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=380486\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> cos(A + B) = [cos(A) * cos(B)] - [sin(A) * sin(B)]\r<BR>\n" );
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document.write( "you can use Pythagoras to find the missing functions<BR>\n" );
document.write( "___ cos(A) = 40 / sqrt(40^2 + 9^2)<BR>\n" );
document.write( "___ sin(A) = 9 / sqrt(40^2 + 9^2)\r<BR>\n" );
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document.write( "B is part of a 3-4-5 triangle , so sin(B) = -3/5\r<BR>\n" );
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document.write( "just figured out that 9-40-? is also a Pythagorean triple </SPAN>\n" );
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