document.write( "Question 1012198: A searchlight has a parabolic reflector that forms a “bowl” which is 12 inches wide from rim to rim and 8 inches deep. If the filament of the light bulb is located at the focus, how far from the vertex of the reflector is it? \n" ); document.write( "
Algebra.Com's Answer #628092 by josgarithmetic(39617)\"\" \"About 
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\"4py=x%5E2\" can be a parabola with vertex at the origin, and opening upward. Using different symbols, the parabola can also be \"y=ax%5E2\" and has points (-6,8) and (6,8).\r
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\n" ); document.write( "\n" ); document.write( "Find the factor, a.
\n" ); document.write( "\"8=a%2A6%5E2\", using the simpler formula.
\n" ); document.write( "\"a=8%2F36\"
\n" ); document.write( "\"a=2%2F9\"
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\n" ); document.write( "The equation for the parabola more specifically can be \"highlight%28y=%282%2F9%29x%5E2%29\".\r
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\n" ); document.write( "\n" ); document.write( "What about the focus?
\n" ); document.write( "Put the equation with the p into the same form as the more specific-found equation. The value of p is THE DISTANCE FROM VERTEX TO FOCUS.
\n" ); document.write( "\"4py=x%5E2\"
\n" ); document.write( "\"y=%281%2F%284p%29%29x%5E2\"
\n" ); document.write( "Comparing the corresponding equation parts,
\n" ); document.write( "\"2%2F9=1%2F%284p%29\"
\n" ); document.write( "\"9%2F2=4p\"
\n" ); document.write( "\"p=9%2F%282%2A4%29\"
\n" ); document.write( "\"highlight%28p=9%2F8%29\".\r
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\n" ); document.write( "\n" ); document.write( "The focus will be on the \"opening upward\" side of the parabola, as described in this discussion, above the origin, so the focus is \"highlight%289%2F8=1%261%2F8%29\" inches away from the vertex. Inside of the curve.
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