document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=972724>Question 972724</A>: <I><SPAN STYLE=\"word-break: break-all;\"> if sin  &#960;/3 = &#8730;3\2<BR>\n" );
document.write( "  Cos &#960;/3 = 1/2<BR>\n" );
document.write( "  Sin &#960;/4 = cos &#960;/4 =&#8730;2/2<BR>\n" );
document.write( "Evaluate without the use of an calculator the exact value of cos 7&#960;/12\r<BR>\n" );
document.write( "\n" );
document.write( "I tried using the l.c.m  to get 4&#8730;3/2 but then I got lost </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #594985 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=594985\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> if sin &#960;/3 = &#8730;3\2<BR>\n" );
document.write( "Cos &#960;/3 = 1/2<BR>\n" );
document.write( "Sin &#960;/4 = cos &#960;/4 =&#8730;2/2<BR>\n" );
document.write( "Evaluate without the use of an calculator the exact value of cos 7&#960;/12 <BR>\n" );
document.write( "-----<BR>\n" );
document.write( "Note:: 7pi/12 = 3pi/12 + 4pi/12 = pi/4 + pi/3<BR>\n" );
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document.write( "Your Problem::<BR>\n" );
document.write( "cos(7pi/12) = cos[(pi/4)+(pi/3)] <BR>\n" );
document.write( "-------<BR>\n" );
document.write( "= cos(pi/4)cos(pi/3)-sin(pi/4)sin(pi/3)<BR>\n" );
document.write( "------<BR>\n" );
document.write( "= (1/sqrt(2))(1/2) - (1/sqrt(2))sqrt(3)/2<BR>\n" );
document.write( "------<BR>\n" );
document.write( "= [sqrt(2)/4] - [sqrt(6)/4]<BR>\n" );
document.write( "------<BR>\n" );
document.write( "= [sqrt(2) - sqrt(6)]/4<BR>\n" );
document.write( "-------------------------<BR>\n" );
document.write( "Cheers,<BR>\n" );
document.write( "Stan H. </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );