How to count all the orthogonal transformations?

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SUMMARY

The discussion centers on identifying and counting orthogonal transformations from the plane defined by the equation \(x+y+z=0\) to the plane \(x-y-2z=0\) in \(\mathbb{R}^{3}\). The transformation utilizes the bases \(B\) and \(P\) defined as \(B=\begin{bmatrix} 1 & 1 & 1\\ 1 & -1 & 1\\ 1 & 0 & 2 \end{bmatrix}\) and \(P=\begin{bmatrix} 1 & 1 & 1\\ -1 & 1 & -1\\ -2 & 0 & 1 \end{bmatrix}\). The determinant condition \(det(A_{0})=1\) must be maintained, leading to the conclusion that there are exactly four orthogonal transformations that satisfy the given conditions.

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Homework Statement


Find an orthogonal transformation ##\mathbb{R}^{3}\rightarrow \mathbb{R}^{3}## that map plane ##x+y+z=0## into ##x-y-2z=0## and vector ##v_{1}=(1,-1,0)## into ##(1,1,0)##. Count all of them!

Homework Equations


##A_{S}=PA_{0}B^{-1}##

The Attempt at a Solution


So basis ##B=\begin{bmatrix}
1 & 1 & 1\\
1& -1 & 1\\
1& 0& 2
\end{bmatrix}## and ##P=\begin{bmatrix}
1 & 1 & 1\\
-1& 1 & -1\\
-2& 0& 1
\end{bmatrix}## where the last vector in both basis is a vector product of ##n_{1} \times v_{1}##

##A_{0}=diag(1,1,1)## and ##A_{S}=PA_{0}B^{-1}##

Now, how do I count them? What do they represent - meaning, how do they differ from this one? O.o please help.
 
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So whatever I do, ##det(A_{0})=1## has to stay the same, where ##A_{0}=diag(1,1,1)##. Meanin I could also use ##A_{0}=diag(-1,-1,1)## or ##A_{0}=diag(-1,1,-1)## or ##A_{0}=diag(1,-1,-1)##, right?

To sum up, there are 4 orthogonal transformations that do that?
 

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