Excerpt from Multilinear Functions of Direction: And Their Uses in Differential GeometryThe theory of multilinear functions does not merely coordinate. It affords simple proofs of the relations between the cubic functions of Laguerre and Barboux and of formulae 7851, 7352) for the twist of a family of surfaces, and it leads naturally to expressions (7241) for the rates of change of the two principal curvatures of a variable member of a family of surfaces at the current point of an orthogonal trajectory of the family, expres sions that are interesting because their existence was deduced by Forsyth in 1903 from an enumeration of invariants.About the PublisherForgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.comThis book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully, any imperfections that remain are intentionally left to preserve the state of such historical works.