document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=174693>Question 174693</A>This question is from textbook <A HREF=http://www.amazon.com/exec/obidos/ASIN/9781567655568/algebrahomeworkh>Amsco's Preparing for the Regents Examination Mathematics B</A><BR>\n" );
document.write( ": <I><SPAN STYLE=\"word-break: break-all;\"> 14) If cos y = -4/5 when 90degrees < y < 180degrees, find the value of sin(2y).\r<BR>\n" );
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document.write( "show work thanks\r<BR>\n" );
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document.write( "happy new years =) </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #129742 by </B><A HREF=/tutors/aboutme.mpl?userid=jim_thompson5910><B>jim_thompson5910(35256)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=jim_thompson5910><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=129742\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> If cos y = -4/5, then the adjacent side is 4 units and the hypotenuse is 5 units. So the other leg is <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=sqrt%285%5E2-4%5E2%29=sqrt%2825-16%29=sqrt%289%29=3 ALIGN=MIDDLE  ALT=\"sqrt%285%5E2-4%5E2%29=sqrt%2825-16%29=sqrt%289%29=3\"   DISABLED_style= \"max-width:90%; height:auto;\" > units. In other words, this triangle has side lengths of 3, 4, and 5 units.\r<BR>\n" );
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document.write( "So sin(y) = opposite/hypotenuse = 3/5\r<BR>\n" );
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document.write( "Note: sine is positive since 90 < y < 180\r<BR>\n" );
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document.write( "So\r<BR>\n" );
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document.write( "sin(2y) = 2*sin(y)*cos(y)\r<BR>\n" );
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document.write( "sin(2y) = 2*(3/5)*(-4/5) ... Plug in sin(y) = 3/5  and cos y = -4/5\r<BR>\n" );
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document.write( "sin(2y) = -24/25 </SPAN>\n" );
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