Matrix of singular transformation A=(0,1) to A'=(0,0),\ B=(2,0) to B'=(0,1) and

Emmy Combs

Emmy Combs

Answered question

2022-01-20

Matrix of singular transformation
A=(0,1) to A=(0,0), B=(2,0) to B=(0,1) and C=(2,1) to C=(0,2)
find the matrix representation r?

Answer & Explanation

tsjutten20

tsjutten20

Beginner2022-01-21Added 13 answers

Step 1
The map can be expressed as
[xy]=[a11a12a21a22][xy]+[b1b2]
For the non-singular case, you should be able to solve for the 6 unknowns (aij, bi) using the 6 equations that you have:
0=a11(0)+a12(1)+b1
0=a21(0)+a22(1)+b2
0=a11(2)+a12(0)+b1
1=a21(2)+a22(0)+b2
0=a11(2)+a12(1)+b1
2=a21(2)+a22(1)+b2
In matrix form:
[000102]=[010010000101200010002001002101][a11a12a21a22b1b2]
For the singular case you will need to compute a pseudoinverse to find the unknowns. For the data you have provided an inverse appears to exist and you don't need a pseudoinverse.
nebajcioz

nebajcioz

Beginner2022-01-22Added 15 answers

Step 1
Let
g(x)=Mx+b
If g is affine, it can always be written in this form.
We just to determine M,b
Since A+BC=0 (and 1+11=1) we have
g(0)=b=g(A+BC)=g(A)+g(B)g(C)=(0, 1)T
Note that Mx=g(x)b and A, B are linearly independent, so M is completely specified by its behavior on A, B
M(0,1)T=(1,1)T,
M(2,0)T=(0,2)T
hence
M=[0012][0210]1=[0011]
It is straightforward to check that this gives the correct results.
RizerMix

RizerMix

Expert2022-01-27Added 656 answers

Here is a more geometric approach. You can find the linear part of an affine transformation by looking at how it transforms vectors between pairs of points - the translation part of the affine transformation then cancels out. The vector BC is (0, 1). This transforms into the vector \(Brightarrow

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