Derive the equation of a parabola from a focus and directrix.
Derive separate parabola features from focus and directrix
Problem
For a parabola with focus \((0,~2)\) and directrix \(y~=~-2\), project the focus perpendicularly to the directrix and take the midpoint for the vertex. Report the axis, signed focal parameter \(p\), opening direction, and equal-distance check.
A parabola’s main features come from one perpendicular focus-to-directrix construction. We’ll project the focus onto the line, take the midpoint for the vertex, use the perpendicular orientation for the axis, read signed p toward the focus, infer the opening, and confirm equal defining distances at the vertex.
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