document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=438552>Question 438552</A>: <I><SPAN STYLE=\"word-break: break-all;\"> If &#415; is in quadrant IV and sin &#415;= -2/3 find the exact value of cos(&#415;/2) </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #303256 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=303256\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> If &#415; is in quadrant IV and sin &#415;= -2/3 find the exact value of cos(&#415;/2)<BR>\n" );
document.write( "..<BR>\n" );
document.write( "sinx=-2/3<BR>\n" );
document.write( "cos^2x=1-sin^2x=1-4/9=9/9-4/9=5/9<BR>\n" );
document.write( "cosx=sqrt(5/9)=sqrt(5)/3=.74536<BR>\n" );
document.write( "Trig identity for cos (x/2) (half-angle formula)<BR>\n" );
document.write( "cos(x/2)=+-sqrt((1+cosx)/2))  (use + value since cos is + in quadrant IV)<BR>\n" );
document.write( "             =sqrt((1+.74536)/2))<BR>\n" );
document.write( "             =sqrt(.87268)<BR>\n" );
document.write( "             =.93417 <BR>\n" );
document.write( "ans:<BR>\n" );
document.write( "cos(x/2)=.93417 </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );