Question

a parabolic lamp is facing due east. The bulb (located at the focus) is 8 inches away from the vertex (located at the origin). the lamp has a diameter of 20 inches. Which is the depth of the dish?

Answer 1

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Answer:

3 1/8 inches

Explanation:

For focus-vertex distance p, the equation of the parabola can be written ...

y = x^2/(4p)

Here, we have p=8. We want to find the value of y when x=10 (the radius of the dish). That is ...

y = (10^2)/(4·8) = 100/32 = 3 1/8

The dish is 3 1/8 inches deep.