document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=170004>Question 170004</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A parabolic satellite television antenna has a diameter of 6 feet and is 1.6 feet deep. How far is the focus from the vertex?\r<BR>\n" );
document.write( "\n" );
document.write( "I have tried every formula that I can think of to get this one to work out correctly for me and I'm coming up short.\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "Please help.\r<BR>\n" );
document.write( "\n" );
document.write( "Thank you in advance </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #125467 by </B><A HREF=/tutors/aboutme.mpl?userid=stanbon><B>stanbon(75887)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=stanbon><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=125467\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> A parabolic satellite television antenna has a diameter of 6 feet and is 1.6 feet deep. How far is the focus from the vertex?<BR>\n" );
document.write( "----------------------------<BR>\n" );
document.write( "Draw the parabola on an xy coordinate grill.<BR>\n" );
document.write( "Put the vertex at (0,1.6)<BR>\n" );
document.write( "Then the parabola will meet the x-axis at (-3,0) and (3,0)<BR>\n" );
document.write( "----------------<BR>\n" );
document.write( "So the equation of the parabola will be y = -x^2 + 1.6<BR>\n" );
document.write( "or x^2 = -y - 1.6<BR>\n" );
document.write( "or x^2 = -(y+1.6)<BR>\n" );
document.write( "-----------------<BR>\n" );
document.write( "This has the form x^2 = 4p(y-k), so 4p = -1 and p = -1/4<BR>\n" );
document.write( "---<BR>\n" );
document.write( "The distance from the vertex to the focus is p so the <BR>\n" );
document.write( "focus is at y = 1.6-(1/4) = 1.6-0.25 = 1.375<BR>\n" );
document.write( "-------------------<BR>\n" );
document.write( "Ans: the focus is (1/4) ft. from the vertex.<BR>\n" );
document.write( "======================<BR>\n" );
document.write( "Cheers,<BR>\n" );
document.write( "Stan H.\r<BR>\n" );
document.write( "\n" );
document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );