#
Where Two Orthogonal Normals Meet

If two of the normals which can be drawn to a parabola, through a point
are at right angles, the locus of that point is parabola.
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Reference: **Isaac
Todhunter,
A
treatise on plane co-ordinate geometry as applied to the straight line
and the conic sections** 1880, p. 141, #45.