- #1
SetepenSeth
- 16
- 0
Homework Statement
Let ##T:M_2 \to M_2## a linear transformation defined by
##T \begin{bmatrix}
a&b\\
c&d
\end{bmatrix} =
\begin{bmatrix}
a&0\\
0&d
\end{bmatrix}##
Describe ##ker(T)## and ##range(T)##, and find their basis.
Homework Equations
For a linear transformation ##T:V\to W##
##range(T)={T(x) \epsilon W : x \epsilon V}##
##ker(T)= {x \epsilon V : T(x)= 0 \epsilon W}##
The Attempt at a Solution
Skipping the first part of the proof, I get to the part where I describe the range of the transformation and express it as a linear combination of two ##M_2## matrix##T \begin{bmatrix}
a&b\\
c&d
\end{bmatrix} =
\begin{bmatrix}
a&0\\
0&d
\end{bmatrix}##
##T \begin{bmatrix}
a&b\\
c&d
\end{bmatrix} =
a\begin{bmatrix}
1&0\\
0&0
\end{bmatrix}+
d\begin{bmatrix}
0&0\\
0&1
\end{bmatrix}
##
So $$\begin{bmatrix}
1&0\\
0&0
\end{bmatrix} and \begin{bmatrix}
0&0\\
0&1
\end{bmatrix}$$ span the range for ##T##, also they are linearly independent, thus forming a basis for the range.
The kernel can be expressed as
##ker(T)={A \epsilon M_2 : Ax=0 \epsilon M_2}##
##ker(T)=A \epsilon M_2 :## ##A =
\begin{bmatrix}
a&b\\
c&d
\end{bmatrix} \forall a,b,c,d \epsilon ℝ, a=d=0## If I got it right up to this point then
##dim[range(T)]=2##
But then according to the theorem that says
##dim[range(T)]+dim[ker(T)]=dim(V)##
Being ##V## the space of ##2_x####2## square matrix, then ##dim(V)=2## but that would make ##dim[ker(T)]=0## which doesn't make sense to me, so I believe I got a concept wrong somewhere on my analysis.
Any advise would be appreciated.