A Dish TV satellite dish is the shape of a paraboloid. The dish is 42 inches wide, and 10 inches deep. How many inches should the receiver be located from the vertex for optimal reception? (round to the nearest thousandth)

1 answer

the cross-section is a parabola
Recall that the parabola
x^2 = 4py
has its vertex at (0,0)
and its focus at y = p
You want y(21) = 10
That will give you the value of p you need.