document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=847482>Question 847482</A>: <I><SPAN STYLE=\"word-break: break-all;\"> given that A is obtuse and that tan A= -1/2, find the value of cos A and of sin A<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 #510471 by </B><A HREF=/tutors/aboutme.mpl?userid=swincher4391><B>swincher4391(1107)</B></A><img src=\"/images/stars/stars-12.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=swincher4391><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=swincher4391><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=510471\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> tan A = - 1/2<BR>\n" );
document.write( "tan^-1 A = tan^-1(-1/2) = -26.56 degrees\r<BR>\n" );
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document.write( "We know that A is between 0 and 180 degrees, so the angle formed with 180 is 180 - 26.56 = 153.48 degrees.\r<BR>\n" );
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document.write( "From there we can find sin(153.48 degrees ) = 0.45  and cos(153.48 degrees) = -0.89. \r<BR>\n" );
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document.write( "Let's check and make sure this works.\r<BR>\n" );
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document.write( "We know tan(A) can only be negative in the 2nd and 4th quadrants. Since we're only concerned with the 1st and 2nd quadrants, we know that A must be in the 2nd quadrant. In the 2nd quadrant we expect that cos(A) is negative while sin(A) is positive since cosine refers to our x position while sine refers to our y position. The signs of our answers are in line with this. We also know tan(A) = sin(A)/cos(A). So 0.45/-0.89  = -.5056 which is close enough to -1/2. I'm okay with this because this was a result of rounding. </SPAN>\n" );
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