document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1192245>Question 1192245</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Find the expression for tan3x in term of tan(x) only<BR>\n" );
document.write( "tan3x = (sin3x/cos3x)\r<BR>\n" );
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document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #824146 by </B><A HREF=/tutors/aboutme.mpl?userid=Alan3354><B>Alan3354(69443)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Alan3354><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=Alan3354><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=824146\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> duplicate<BR>\n" );
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document.write( "Picking an angle and checking that the formula is correct does NOT necessarily mean it is correct for all angles.<BR>\n" );
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document.write( "RE:  the formula:<BR>\n" );
document.write( "If it is not correct for any angle tested, it is not valid.<BR>\n" );
document.write( "It it is correct for any angle(s), it might be valid, might not be.<BR>\n" );
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document.write( "As an example:<BR>\n" );
document.write( "Prove sin(x) = cos(x)<BR>\n" );
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document.write( "Let x = 45 degs<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=sqrt%282%29%2F2+=+sqrt%282%29%2F2 ALIGN=MIDDLE  ALT=\"sqrt%282%29%2F2+=+sqrt%282%29%2F2\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "QED<BR>\n" );
document.write( "sin(x) <> cos(x) in general.<BR>\n" );
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document.write( "It's possible the other tutor knew that formula from memory, but not likely.<BR>\n" );
document.write( "He probably looked it up, as you could have done.<BR>\n" );
document.write( "There are WAAAAYYYY too many formulas for anyone to remember, IMO. </SPAN>\n" );
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