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For a rectifiable curve these approximations don't get arbitrarily large (so the curve has a finite length). If a curve can be parameterized as an injective and continuously differentiable function (i.e., the derivative is a continuous function) f : [ a , b ] → R n {\displaystyle f\colon [a,b]\to \mathbb {R} ^{n}} , then the curve is ...
The coordinate-independent definition of the square of the line element ds in an n-dimensional Riemannian or Pseudo Riemannian manifold (in physics usually a Lorentzian manifold) is the "square of the length" of an infinitesimal displacement [2] (in pseudo Riemannian manifolds possibly negative) whose square root should be used for computing curve length: = = (,) where g is the metric tensor ...
This can be done by partitioning the interval [a, b] into n sub-intervals [t i−1, t i] of length Δt = (b − a)/n, then r(t i) denotes some point, call it a sample point, on the curve C. We can use the set of sample points { r ( t i ): 1 ≤ i ≤ n } to approximate the curve C as a polygonal path by introducing the straight line piece ...
Clearly the radius will not depend on the position γ(t), only on the velocity γ′(t) and acceleration γ″(t). There are only three independent scalars that can be obtained from two vectors v and w, namely v · v, v · w, and w · w. Thus the radius of curvature must be a function of the three scalars | γ′(t) | 2, | γ″(t) | 2 and γ ...
Other lengths may be used—such as 100 metres (330 ft) where SI is favoured or a shorter length for sharper curves. Where degree of curvature is based on 100 units of arc length, the conversion between degree of curvature and radius is Dr = 18000/π ≈ 5729.57795 , where D is degree and r is radius.
An intrinsic definition of the Gaussian curvature at a point P is the following: imagine an ant which is tied to P with a short thread of length r. It runs around P while the thread is completely stretched and measures the length C(r) of one complete trip around P. If the surface were flat, the ant would find C(r) = 2πr.
Let r = r(t) be the parametric equation of a space curve. Assume that this is a regular parametrization and that the curvature of the curve does not vanish. Analytically, r(t) is a three times differentiable function of t with values in R 3 and the vectors ′ (), ″ are linearly independent.
In other words, if γ 1 (t) and γ 2 (t) are two curves in such that for any t, the two principal normals N 1 (t), N 2 (t) are equal, then γ 1 and γ 2 are Bertrand curves, and γ 2 is called the Bertrand mate of γ 1. We can write γ 2 (t) = γ 1 (t) + r N 1 (t) for some constant r. [1]