document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=445781>Question 445781</A>: <I><SPAN STYLE=\"word-break: break-all;\"> If x is a positive acute angle and cosx = 1/9, what is the value of cos 1/2x? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #307243 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=307243\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> If x is a positive acute angle and cosx = 1/9, what is the value of cos 1/2x?<BR>\n" );
document.write( "..<BR>\n" );
document.write( "Use half-angle formula for cosine with positive sqrt because x/2 is positive<BR>\n" );
document.write( "cos(x/2)=sqrt((1+cosx)/2)<BR>\n" );
document.write( "             =sqrt((1+1/9)/2)    <BR>\n" );
document.write( "             =sqrt((10/9)/2)<BR>\n" );
document.write( "             =sqrt(5/9)<BR>\n" );
document.write( "cos(x/2)=&#8730;5/3 (ans) </SPAN>\n" );
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