document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=868779>Question 868779</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A field microphone has a parabolic cross section. It is 20 in wide at the opening and its focus is 2 in from the vertex. How deep is the microphone at the vertex? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #523886 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=523886\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> A field microphone has a parabolic cross section. It is 20 in wide at the opening and its focus is 2 in from the vertex. How deep is the microphone at the vertex?<BR>\n" );
document.write( "***<BR>\n" );
document.write( "representing the parabolic cross section of the microphone, consider a parabola that opens upwards with vertex at the origin.<BR>\n" );
document.write( "Its basic form of equation: x^2=4py<BR>\n" );
document.write( "For given parabola:<BR>\n" );
document.write( "p=2 (distance from focus to vertex on the axis of symmetry<BR>\n" );
document.write( "4p=8<BR>\n" );
document.write( "equation:x^2=8y<BR>\n" );
document.write( "solve for y with x=10<BR>\n" );
document.write( "y=x^2/8=100/8=12.5<BR>\n" );
document.write( "How deep is the microphone at the vertex? 12.5 in </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );