N-curve: Difference between revisions
No edit summary |
No edit summary |
||
Line 96: | Line 96: | ||
This new curve has the same initial and end points as α. |
This new curve has the same initial and end points as α. |
||
===Example of ''n''-curving=== |
===Example 1 of ''n''-curving=== |
||
Let ρ denote the [[Rhodonea curve]] <math> r = \cos(2\theta)</math>, which is a loop at 1. Its parametric equations are |
Let ρ denote the [[Rhodonea curve]] <math> r = \cos(2\theta)</math>, which is a loop at 1. Its parametric equations are |
||
Line 115: | Line 115: | ||
It is a curve that starts at the point (0, 1) and ends at (2π, 1). |
It is a curve that starts at the point (0, 1) and ends at (2π, 1). |
||
[[File:N-curving.gif|thumb|450px|center|Notice how the curve starts with a [[cosine]] curve at ''N''=0. Please note that the parametric equation was modified to center the curve at origin.]] |
[[File:N-curving.gif|thumb|450px|center|Notice how the curve starts with a [[cosine]] curve at ''N''=0. Please note that the parametric equation was modified to center the curve at origin.]] |
||
===Example 2 of n-curving === |
|||
Let χ denote the [[Cosine Curve]] |
|||
: <math> \chi(t) = 2\pi t +i\cos(2\pi t), 0\leq t \leq 1 </math> |
|||
With another [[Rhodonea Curve]] |
|||
:<math> \rho = \cos(3 \theta) </math> |
|||
we shall ''n''-curve the cosine curve. |
|||
The rhodonea curve can also be given as |
|||
: <math> \rho(t) = \cos(6\pi t)[\cos (2\pi t)+ i\sin(2\pi t)], 0\leq t \leq 1 </math> |
|||
The curve <math>\phi_{\rho_{n},e}(\chi)</math> has the parametric equations |
|||
: <math> x=2\pi t + 2\pi [\cos( 6\pi nt)\cos(2\pi nt)- 1], \quad y=\cos(2\pi t) + 2\pi \cos( 6\pi nt)\sin(2 \pi nt), 0\leq t \leq 1 </math> |
|||
See the figure for <math>n = 15 </math>. |
|||
[[File:CosineRhodonea.jpg]] |
|||
===Generalized n-Curving=== |
===Generalized n-Curving=== |
||
In the FTA ''C''[0, 1] of curves, instead of ''e'' we shall take an arbitrary curve <math>\beta</math>, a loop at 1. |
In the FTA ''C''[0, 1] of curves, instead of ''e'' we shall take an arbitrary curve <math>\beta</math>, a loop at 1. |
Revision as of 00:08, 1 January 2011
![]() |
This article needs additional citations for verification. (October 2009) |
We take the functional theoretic algebra C[0, 1] of curves. For each loop γ at 1, and each positive integer n, we define a curve called n-curve. The n-curves are interesting in two ways.
- Their f-products, sums and differences give rise to many beautiful curves.
- Using the n-curves, we can define a transformation of curves, called n-curving.
Multiplicative inverse of a curve
A curve γ in the functional theoretic algebra C[0, 1], is invertible, i.e.
exists if
If , where , then
The set G of invertible curves is a non-commutative group under multiplication. Also the set H of loops at 1 is an Abelian subgroup of G. If , then the mapping is an inner automorphism of the group G.
We use these concepts to define n-curves and n-curving.
n-Curves and their products
If x is a real number and [x] denotes the greatest integer not greater than x, then
If and n is a positive integer, then define a curve by
is also a loop at 1 and we call it an n-curve. Note that every curve in H is a 1-curve.
Suppose Then, since .
Example 1: Product of the astroid with the n-curve of the unit circle
Let us take u, the unit circle centered at the origin and α, the astroid. The n-curve of “u” is given by,
and the astroid is
The parametric equations of their product are
See the figure.
Since both are loops at 1, so is the product.
![]() |
![]() |
Example 2: Product of the unit circle and its n-curve
The unit circle is
and its n-curve is
The parametric equations of their product
are
See the figure.
Example 3: n-Curve of the Rhodonea minus the Rhodonea Curve
Let us take the Rhodonea Curve
If denotes the curve,
The parametric equations of are
n-Curving
If , then, as mentioned above, the n-curve . Therefore the mapping is an inner automorphism of the group G. We extend this map to the whole of C[0, 1], denote it by and call it n-curving with γ. It can be verified that
This new curve has the same initial and end points as α.
Example 1 of n-curving
Let ρ denote the Rhodonea curve , which is a loop at 1. Its parametric equations are
With the loop ρ we shall n-curve the cosine curve
The curve has the parametric equations
See the figure.
It is a curve that starts at the point (0, 1) and ends at (2π, 1).
![](http://upload.wikimedia.org/wikipedia/commons/thumb/1/1b/N-curving.gif/450px-N-curving.gif)
Example 2 of n-curving
Let χ denote the Cosine Curve
With another Rhodonea Curve
we shall n-curve the cosine curve.
The rhodonea curve can also be given as
The curve has the parametric equations
See the figure for .
Generalized n-Curving
In the FTA C[0, 1] of curves, instead of e we shall take an arbitrary curve , a loop at 1. This is justified since
Then, for a curve γ in C[0, 1],
and
If , the mapping
given by
is the n-curving.
We get the formula
Thus given any two loops and at 1, we get a transformation of curve
- given by the above formula.
This we shall call generalized n-curving.
Example 1
Let us take and as the unit circle ``u.’’ and as the cosine curve
Note that
The transformed curve has the parametric equations
For the transformed curves, see the figure.
See also
References
- Sebastian Vattamattam, "Transforming Curves by n-Curving", in Bulletin of Kerala Mathematics Association, Vol. 5, No. 1, December 2008