document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1056981>Question 1056981</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Hi, can someone help me in the 2nd part to find x.\r<BR>\n" );
document.write( "\n" );
document.write( "Question:<BR>\n" );
document.write( "By writing cos 4x = cos (3x+x) and cos 2x = cos (3x-x), show that cos 2x + cos 4x = 2cos3xcosx and cos 2x – cos 4x = 2sin3xsinx.\r<BR>\n" );
document.write( "\n" );
document.write( "Given further that cos3xcosx = 0.683 and sin3xsinx = 0.183, find the value of x where 0° < x < 180°.\r<BR>\n" );
document.write( "\n" );
document.write( "Thank you very much. </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #672084 by </B><A HREF=/tutors/aboutme.mpl?userid=josgarithmetic><B>josgarithmetic(39630)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=josgarithmetic><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=672084\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=highlight_green%28cos%28x%2By%29=cos%28x%29cos%28y%29-sin%28x%29sin%28y%29%29 ALIGN=MIDDLE  ALT=\"highlight_green%28cos%28x%2By%29=cos%28x%29cos%28y%29-sin%28x%29sin%28y%29%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=highlight_green%28cos%28x-y%29=cos%28x%29cos%28y%29%2Bsin%28x%29sin%28y%29%29 ALIGN=MIDDLE  ALT=\"highlight_green%28cos%28x-y%29=cos%28x%29cos%28y%29%2Bsin%28x%29sin%28y%29%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "-----------------------------------------------------\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=cos%282x%29%2Bcos%284x%29=2cos%283x%29cos%28x%29 ALIGN=MIDDLE  ALT=\"cos%282x%29%2Bcos%284x%29=2cos%283x%29cos%28x%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=cos%283x-x%29%2Bcos%283x%2Bx%29 ALIGN=MIDDLE  ALT=\"cos%283x-x%29%2Bcos%283x%2Bx%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=cos%283x%29cos%28x%29%2Bsin%283x%29sin%28x%29%2Bcos%283x%29cos%28x%29-sin%283x%29sin%28x%29 ALIGN=MIDDLE  ALT=\"cos%283x%29cos%28x%29%2Bsin%283x%29sin%28x%29%2Bcos%283x%29cos%28x%29-sin%283x%29sin%28x%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "Using commutative property of equality,<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=cos%283x%29cos%28x%29%2Bcos%283x%29cos%28x%29%2Bsin%283x%29sin%28x%29-sin%283x%29sin%28x%29 ALIGN=MIDDLE  ALT=\"cos%283x%29cos%28x%29%2Bcos%283x%29cos%28x%29%2Bsin%283x%29sin%28x%29-sin%283x%29sin%28x%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=2cos%283x%29cos%28x%29=RightHandSide ALIGN=MIDDLE  ALT=\"2cos%283x%29cos%28x%29=RightHandSide\"   DISABLED_style= \"max-width:90%; height:auto;\" >\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "Very straightforward if you know or have reference to the two identities.\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "--<BR>\n" );
document.write( "The second part if you will look carefully, only depends on simple substitution.   Note also that the sine information in not needed. </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );