Titlebook: Elementary Topics in Differential Geometry; J. A. Thorpe Textbook 1979 Springer-Verlag New York Inc. 1979 Differentialgeometrie.Isometrie.

河流

conspicuous

Curvature of Surfaces,easures the turning of the normal as one moves in S through . with various velocities .. Thus . measures the way . curves in ?.. at .. For . = 1, we have seen that . is just multiplication by a number .(p) the curvature of . at .. We shall now analyze . when . > 1.

Inflamed

Convex Surfaces,ee Figure 13.1). An oriented .-surface . is . at . ∈ . if there exists an open set . ? ?.. containing . such that . ∩ . is contained either in . or in .. Thus a convex .-surface is necessarily convex at each of its points, but an .-surface convex at each point need not be a convex .-surface (see Figure 13.2).

輕彈

顯而易見

無力更進(jìn)

支架

https://doi.org/10.1007/978-1-349-18756-0The tool which will allow us to study the geometry of level sets is the calculus of vector fields. In this chapter we develop some of the basic ideas.

閃光你我

Let .: . → ? be a smooth function, where . ? ?.. is an open set. let . ∈ ? be such that .(.) is non-empty, and let . ∈ .(.). A vector at . is said to be . .(.) if it is a velocity vector of a parametrized curve in ?.. whose image is contained in .(.) (see Figure 3.1).

摸索

Paul Kamudoni,Nutjaree Johns,Sam SalekA .. in ?.. is a non-empty subset . of ?.. of the form . = .(.) where .: . → ?, . open in ?.. is a smooth function with the properly that ?.(.) ≠ . for all . ∈ .. A 1-surfacc in ?. is also called a .. A 2-surface in ?. is usually called simply a .. An .-surface in ?.. is often called a .. especially when . > 2.

燦爛

In Search of a New Left, Then and Now,A . . . . ? ?. is a function which assigns to each point . in . a vector .(.) ∈ ? . at .. If .(.) is tangent to . (i.e., .(.) ∈ .) for each . ∈ ., . is said to be a . on .. If .(.) is orthogonal to . (i.e.. .(.) ∈ .) for each . ∈ ., . is said to be a . (see Figure 5.1).