# DIRECTLY

, in Geometry: we say two lines lie directly against each other, when they are parts of the same right line. Also quantities are said to be directly proportional, when the proportion is according to the order of the terms; in contradistinction to inversely, or reciprocally proportional, which is taking the proportion contrary to the order of the terms.

In Mechanics, a body is said to strike or impinge directly against another body, when the stroke is in a direction perpendicular to the surface at the point of impact.

And a sphere in particular strikes directly against another, when the line of direction passes through both their centres.

DIRECTRIX. See Dirigent.

Directrix

, in a Parabola, a line perpendicular to the axis produced, at the distance of the focus without the vertex.

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Entry taken from A Mathematical and Philosophical Dictionary, by Charles Hutton, 1796.

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