Question Example Step by Step The light from the lamp shown has parabolic cross sections. Enter an equation for a cross section of the light if the bulb is 3 inches from the vertex and the vertex is placed at the origin. (Hint The bulb of the lamp is the focus of the parabola.) Suppose the lamp is pointing straight up. The value of p is the distance from the focus to the vertex, or 3 inches. The equation of the parabola is y =