636
Molesworth’s pocket-book
Conic Sections—continued.
Symbol.
I
n
N
t
T
R
V,v
W
x
• y
z
Definition.
Parameter.—A third proportion to any dia-
meter and its conjugate; or D ; d d; I
I (Fig- ?)• ,
Subnormal.—The portion of the transverse
axis subtended by the normal (Fig. 10).
Normal.—A line drawn at right angles to a
tangent from the tangent point to the trans-
verse axis (Fig. 10).
Subtangent.—That part of the transverse
axis that is subtended by the tangent
(Fig. 10).
Tangent.—A right line which touches the
curve, and, being produced, does not cut
j it. The length of the tangent is limited
between the point of contact and the
j '• transverse axis.
I Radius of Curvature at any point of the
curve. .
Radii Vectores.—The radius vector is a
straight line drawn from the focus to any
point in the curve (Fig. 11).
! Traced Angle.—The angle formed by the
radius vector and the transverse axis
(Fig. 11). ,
Abscissa. — The portion of the diameter
which is between the ordinate and the
curve. , , .
Ordinate.—Any line parallel to the tangent
of a diameter, and drawn from that dia-
meter to the curve (Fig. 12).
Distance from Centre of curve to any
ordinate (Fig. 12).