Let's start with definitions:
For given curve $C(x(t),y(t))$ in $R^2$ when $t\in[a,b]$.
Cartan's signature that defined in the following way: $\{\kappa.\kappa_s\}$ when $\kappa$ is invariant curvature of the curve, $s$ is invariant acrlength and $\kappa_s$ is derived of curvature by acrlength. Let's denote Cartan's signature of curve $C$ as $S(C)$.
Euclidean/Equi-affine transform is transform from $R^2$ to $R^2$ such $T(v) = A v + t$ when $v$ is each point of the curve, $t$ is constant and for Euclidean transform $A^TA=AA^T=Id$ and for Equi-affine transform $\det(A)=1$
Let's denote Curve $C$ after Euclidean transform as $\hat C$ and after Equi-affine transform as $\bar C$
I'm looking for any information if curve Cartan's signature is the same after Euclidean transform and after Equi-affine transform.
I mean $S(C)=S(\hat C)$ is it true? and this one $S(C)=S(\bar C)$?
sorry if something not clear, I did my best.
It's kind of thoeretical part of this question:

EDIT
My results to original question:
- Euclidean transform keep Cartan's signature
- Equi-affine transform change Cartan's signature
but it based on numerical results of couple of examples.
the curve that I worked with is $[cos(t),sin(t)+0.2*sin(t)^2]$ when $t\in[0,2\pi)$ in sampled in 1000 points uniformly.
Curve after Euclidean transform $
A = \begin{pmatrix}
cos(\theta) & sin(\theta) \\
-sin(\theta) & cos(\theta)
\end{pmatrix};
b = \begin{pmatrix}
1 \\
-1
\end{pmatrix}
$ when $\theta = \pi/4$

Cartan's signature after Euclidean transform

Curve after Equi-affine transform $
A = \begin{pmatrix}
1 & 1 \\
0.5 & 1.5
\end{pmatrix};
b = \begin{pmatrix}
1 \\
-1
\end{pmatrix}$

Cartan's signature after Equi-affine transform


