document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=479877>Question 479877</A>: <I><SPAN STYLE=\"word-break: break-all;\"> How do I find the exact value of sin(5pi/8)? I don't know how to start this one. Do I use a double angle or half angle formula? 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 #328792 by </B><A HREF=/tutors/aboutme.mpl?userid=lwsshak3><B>lwsshak3(11628)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=lwsshak3><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=328792\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> How do I find the exact value of sin(5pi/8)? I don't know how to start this one. Do I use a double angle or half angle formula?<BR>\n" );
document.write( "**<BR>\n" );
document.write( "What you want to do here is to come up with a denominator like 2, 3, 4, & 6 that divides into 180º evenly to a special angle like 30º, 45º, 60º, etc. The half-angle formula for sin will do it.<BR>\n" );
document.write( "..<BR>\n" );
document.write( "sin x/2=±&#8730;((1-cos x)/2) (note that we are doubling the angle in the radical)<BR>\n" );
document.write( "For given problem:<BR>\n" );
document.write( "sin (5&#960;/8)/2=±&#8730;(1-cos(5&#960;/4)/2)<BR>\n" );
document.write( "cos(5&#960;/4)=-&#8730;2/2 (note:5&#960;/4 is in quadrant III where cos is negative)<BR>\n" );
document.write( "sin (5&#960;/8)=&#8730;((1+&#8730;2/2)/2)=&#8730;((2+&#8730;2)/4)=&#8730;(2+&#8730;2)/2 (note: 5&#960;/8) is in quadrant II where<BR>\n" );
document.write( "sin is positive, so we choose the positive root)<BR>\n" );
document.write( "ans:<BR>\n" );
document.write( "sin (5&#960;/8)=&#8730;(2+&#8730;2)/2  </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );