Conversely, two tangents which intersect on the directrix are perpendicular. The geometrical lectures contain some new ways of determining the areas and tangents of curves. In Riemannian geometry, the metric tensor is used to define the angle between two tangents. There are several ways of selecting interpolating tangents for each data point. A "dual parabola" consists of the set of tangents of an ordinary parabola. In case of formula 266 there are no pairs of orthogonal tangents. Closely related to vertical tangents are vertical cusps. Loosely speaking, first order derivatives are related to tangents of curves. It represented one of the earliest methods for constructing tangents to curves. You get on these tangents, and you find new directions. The prescribed initial and terminal tangents correspond to initial and terminal headings. The verticesformula 124, having vertical tangents, are not covered by the representation. There is no need to guess tangents to the measures Signal. Several of Froese's tracks from "Tangents" are included as well. His novelization of "" includes many tangents and new information.