UNIT IV Linear Transformation
UNIT IV Linear Transformation
Pune
Unit IV
Linear Transformation
Introduction
In this chapter we shall study functions from and standard (arbitrary)
vector space to another standard (arbitrary) vector space and its various
properties. The aim of such study is to show how a linear transformation
(mapping or function) can be represented by a matrix. The matrix of a
linear transformation is uniquely determined for a standard (particular)
basis.
Solution : Let u ( x1 , y1 ) v ( x2 , y2 ) R 2
(i ) Here u v ( x1 x2 , y1 y2 )
Consider T (u v) T (( x1 x2 ), ( y1 y2 ))
( x1 x2 y1 y2 , x1 x2 )
and T (u ) T (v) T ( x1 , y1 ) T ( x2 , y2 )
( x1 y1 , x1 ) ( x2 y2 , x2 )
( x1 y1 x2 y2 , x1 x2 )
( x1 x2 y1 y2 , x1 x2 )
Therefore T (u v) T (u ) T (v)
(ii ) Here k .u k ( x1 , y1 ) (kx1 , ky1 )
Consider T (k .u ) T (kx1 , ky1 ) (kx1 ky1 , kx1 )
and kT (u ) kT ( x1 , y1 ) k ( x1 y1 , x1 ) (kx1 ky1 , kx1 )
T (k .u ) kT (u )
Hence T is linear transformation.
Examples:
(i) Let 𝑇: 𝑅 2 → 𝑅 2 be defined as T(x, y) = (x + 1, y + 2) Determine whether T is
a linear transformation.
1
1 2 3 4
1 2 1 3 4
1
x1
1 2 3 1
Ax b
1
x
2
1 2 1
x3
1 2 3 1 1 2 3 1
A | B R2 R1 .
1 2 1 1 0 4 4 0
This gives 4x2 4x3 0, x1 2x2 3x3 1.
Let x3 t R, then x2 t , x1 1 t.
1 t
Thus x t , t R.
t
Example : Let A 68 matrix.Find the values of a and b,
such that T : R a R b defind by T( x) Ax is well defined.
1 1 2
1 1 2
Let a b a 3, b 1
2 1 1
1 1 2
3 .But T is a linear transformation
2 1 1
1 1 2
T 3T T
2 1 1
3(2 x 2 x ) (2 x) 4 2 x 6 x .
2 2
Matrix of a Linear Transformation
1 0 0
1 3 0
T(e1 ) T 0 , T(e2 ) T 1 , T(e1 ) T 0 .
0 2 0 1 1 0
1 3 0
T A T(e1 ) T(e 2 ) T(e3 ) .
2 1 0
dp
Example : T : P3 P2 be a linear transformation defined by T ( p( x)) p( x).
dx
Find the matrix of the linear transformation.
0 1 0 0
A 0 0 2 0 ( th e m a trix o f tra n s fo rm a tio n )
0 0 0 3
a b
T : M 2 (R) P3 , T ax bx cx d ,
3 2
c d
find the matrix of the linear transformation.
1 0 0 0
0 1 0
0
T 0 0 1 0
0 0 0 1
Kernel and Range of a Linear Transformation
Definition: Kernel of a linear transformation (Null space): Let T : V → W be
a linear transformation, then the set of all vectors in V which maps into 0
is called the Kernel of T. It is denoted by ker(T).
i.e., ker(T) = {u ∈ V : T(u) = 0}.
Theorem
Let T : V → W be linear transformation then
(a) The kernel of T is a subspace of V.
(b) The range of T is a subspace of W.
Definition: Rank: Let T : V → W be a linear transformation then the
dimension of the range of T is called the rank of T. Notation: Rank(T).
Rank-Nullity(Dimension) Theorem
i.e., for any linear transformation the rank plus nullity is equal to the
dimension of domain vector space.
Example: Let A be a 6×7 matrix with rank 4. What is the dimension of
solution space of AX = 0.
W T(V)
T (u ) T (v) u v OR
u v T (u ) T (v)
x y 2 z 1 1 2
x 2 y 3z 1 x 2 y 3 z
i) Therefore Range, R(T)=span1 1 2
, ,
1 2 3
Rank of [T]=2
Dimension of R(T)=2
Therefore Basis of R(T) is 1 , 1 or 1 , 2 or 1 , 2
1 2 1 3 2 3
Ker (T ) X R 3 | TX 0
x 0
1 1 2
TX 0 y 0
0 1 1
z 0
Rank=2
Therefore system has one parametric solution.
y+z=0 ⟹ y=-z and x-y-2z=0 ⟹ x=z.
Let z=t, t∈ R,
Therefore y=-t and x=t.
1
ker(T ) span
1
1
1
Basis of ker(T)=
1
1
And dimension of Ker(T)=1
Example: Let T : R 2
R
2
be a linear transformation such that
1 0 0
2 1 2
T 0 ,T 1 3 ,T 0 2
0 1 0 1
x
2
Find T y. Hence find the image of under T. Write the
z 1
0
Rank=2, Nullity=1
Rank=2=Dimension of Co-domain
Nullity=1≠0
Therefore T is onto but not one-one.
Invertible/Regular Linear Transformation
2 4 1 5 4 5 / 22 4 / 22
T 3 5 22 0. T 3 2 3 / 22 2 / 22 .
1
22
5 / 22 4 / 22 2 1 / 11
3 / 22 2 / 22 3 6 / 11
2x y
Example: Show that the map T y x y is a linear transformation.
x
Write the matrix of T. Is the transformation regular or non-singular?
1
Justify. If yes find the image of 2 under T
1
x 2x y
Solution: Given T
y x y
x x
u ,v , R
1 2
y y
1 2
x1 x 2 x1 2 x 2 y 1 y 2
T u v T
2
y
1
y 2 x1 x 2 y 1 y 2
(2 x y ) (2 x y ) 2x y 2x y
1
1 1 2 2 1 2 2
(
x1 y 1) ( x 2 y 2)
x1 y 1 x 2 y 2
T (u ) T (v )
2 −1
Matrix of T is [T]=
1 1
[T ] 2 1 3 0
Therefore T is regular
1 1
1 1 1 3 3
1
T 3 1 2 1
2
3 3
1 1
3 3 2 1
Image of 2 under T
1
1 1 2 1 0
3 3
Composite Linear Transformation
T:V U
S: U W
S T:V W
(S T)( v) S(T( v))
S T ST
x
x 2y z
T : R 3 R 2 defined by T y and S : R 2
R 4
defined by
z x 5y z
2y
x x y
S .Which is well defined T Sor S T ? Find the matrix of the same.
y 2x
x y
As T : R R and S : R R , S T is a
3 2 2 4
0 2 2 10 2
1 1 1 2 1 0 7 2
S T S T
2 0 1 5 1 1 4 2
1 0 1 2 1
𝐎𝐫𝐭𝐡𝐨𝐠𝐨𝐧𝐚𝐥 𝐓𝐫𝐚𝐧𝐬𝐟𝐨𝐫𝐦𝐚𝐭𝐢𝐨𝐧:
A linear transformation 𝑇: R𝑛 → R𝑛 defined as T(X)=AX
is said to orthogonal if A is an orthogonal matrix.
𝐎𝐫𝐭𝐡𝐨𝐠𝐨𝐧𝐚𝐥 𝐌𝐚𝐭𝐫𝐢𝐱 ∶
Matrix A is said to be orthogonal matrix if
AA𝑇 = A𝑇 A = I,where I is a 𝑛 × 𝑛 identity matrix.
a b a b
Find the condition on a and b so that the matrix
a b a b
is orthogonal.
a b a b a b a b 1 0
AA I
t
a b a b a b a b 0 1
a b a b b a a b 1 0
2 2
a b b a
a b a b a b b a a b a b
2 2
0 1
2a 2 2b 2 1 and a 2 b 2 0. This gives
1
a=b= .
2
Geometric Linear Transformations in 𝑹𝟐
Reflection
Scaling
Transformation
in 𝑅2 Shearing
Rotation
Projection
Reflection:
1 0 x x
0 1 y y
Scaling:
k 0 x kx
0 k y ky
Shearing :
1 0
1 1
1
0
Rotation
cos sin x x cos y sin
sin
cos y x sin y cos
Example:
Find the transformation which produces shear in
posive X- direction of factor 3, followed by reflection through
the line y=x.
1 3
:- Shear in posive X- direction of factor 3 : A=
0 1
0 1
reflection through the line y=x : B
1 0
0 1 1 3 0 1
The matrix of transformation is BA= .
1 0 0 1 1 3
y1 0 1 x1 x2
Hence the required transformation is Y=
2
y 1 3 2 1
x x 3 x2
Example: Give a geometric description of the linear transformation
defined by the matrix product
1 0
First action is by marix , which is expansion in
0 3
0 1
positive Y -direction of factor 3. is reflection about
1 0
y x. Hence the effect is scaling in positive Y -direction of
factor 3 followed by reflection about y x.
Example:
x x y 1 1
The matrix of transformation T = is A= .
y y 0 1
0 0 1 1
We will first find images of vertices , , and .
0 2 2 0
1 1 0 0 1 1 0 2 1 1 1 3
0 1 0 0 , 0 1 2 2 , 0 1 2 2
1 1 1 1
and .
0 1 0 0
0 1
2
2
0 1
2
0 0
2 3
2
0 1
0 0
Example: Find the matrix of the transformation T : R R which produces 2 2