document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=871610>Question 871610</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Prove: (sin3x/sinx)-(cos3x/cosx)=2<BR>\n" );
document.write( "I cannot seem to figure this proof out. Please help! </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #525677 by </B><A HREF=/tutors/aboutme.mpl?userid=htmentor><B>htmentor(1343)</B></A><img src=\"/images/stars/stars-12.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=htmentor><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=htmentor><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=525677\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Not sure if we are allowed to use the rather obscure identities <BR>\n" );
document.write( "sin(3x) = 3sin(x) - 4sin^3(x)<BR>\n" );
document.write( "cos(3x) = 4cos^3(x) - 3cos(x)<BR>\n" );
document.write( "If not, you can derive them from sum and/or double angle formulas, e.g. sin(3x) = sin(2x+x)<BR>\n" );
document.write( "From here, the proof is straightforward:<BR>\n" );
document.write( "The first term becomes 3 - 4sin^2(x) after dividing by sin(x)<BR>\n" );
document.write( "The second term becomes 3 - 4cos^2(x) after dividing by cos(x)<BR>\n" );
document.write( "So we have 3 + 3 - 4(sin^2(x) + cos^2(x)) = 6 - 4 = 2<BR>\n" );
document.write( "Done. </SPAN>\n" );
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