1 mac 2103 module 10 lnner product spaces i. 2 rev.f09 learning objectives upon completing this...
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![Page 1: 1 MAC 2103 Module 10 lnner Product Spaces I. 2 Rev.F09 Learning Objectives Upon completing this module, you should be able to: 1. Define and find the](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dc95503460f94abebee/html5/thumbnails/1.jpg)
1
MAC 2103
Module 10
lnner Product Spaces I
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2Rev.F09
Learning ObjectivesUpon completing this module, you should be able to:
1. Define and find the inner product, norm and distance in a given inner product space.
2. Find the cosine of the angle between two vectors and determine if the vectors are orthogonal in an inner product space.
3. Find the orthogonal complement of a subspace of an inner product space.
4. Find a basis for the orthogonal complement of a subspace of ⁿ spanned by a set of row vectors. ℜ
5. Identify the four fundamental matrix spaces of an m x n matrix A, and know the column rank of A, the row rank of A, and the rank of A.
6. Know the equivalent statements of an n x n matrix A.
http://faculty.valenciacc.edu/ashaw/ Click link to download other modules.
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3Rev.09
General Vector Spaces II
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Inner Product Spaces, Inner Products, Inner Product Spaces, Inner Products,
Norm, Distance, Fundamental Matrix Spaces, Norm, Distance, Fundamental Matrix Spaces, Rank, and OrthogonalityRank, and Orthogonality
The major topics in this module:
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4Rev.F09
Definition of an Inner Product and Orthogonal Vectors
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A. Inner Product: Let
be any function from into that satisfies the following conditions for any u, v, z in V:
and iff
Then defines an inner product for all u, v in V.
u and v in V are Orthogonal Vectors iff
⟨⋅,⋅⟩:V ×V → °
V ×V °
c) ⟨kru,
rv⟩ =k⟨
ru,
rv⟩,
a) ⟨ru,
rv⟩ =⟨
rv,
ru⟩,
d) ⟨rv,
rv⟩ ≥0, ⟨
rv,
rv⟩= 0
rv =0.
⟨ru,
rv⟩
⟨ru,
rv⟩= 0.
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5Rev.F09
Definition of a Norm of a Vector
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B. Norm: Let
be any function from into that satisfies the following conditions for any u, v in V:
Then defines a norm for all u in V.
The special norm that is induced by an inner product is
⋅ :V → ° + = [0,∞)
V °+
ru
a)ru ≥0, and
ru =0 iff
ru=
r0,
b) sru = s
ru , and
c)ru+
rv ≤
ru +
rv Triangle inequality.
ru = ⟨
ru,
ru⟩.
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6Rev.F09
Definition of the Distance Between Two Vectors
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C. Distance: Let
be any function from into that satisfies the following conditions for any u, v, w in V:
Then defines the distance for all u, v in V.
The special distance that is induced by a norm is
d(⋅,⋅) :V ×V → ° + =[0,∞)V ×V °
+
d(ru,
rv)
d(ru,
rv)=
ru−
rv = ⟨
ru−
rv,
ru−
rv⟩.
a) d(ru,
rv)≥0, and d(
ru,
rv) =0 iff
ru=
rv,
b) d(ru,
rv) =d(
rv,
ru), and
c) d(ru,
rv) ≤d(
ru,
rw) +d(
rw,
rv) Triangle inequality.
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7Rev.F09
How to Find an Inner Product, Norm, and Distance for Vectors in ⁿℜ ?
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For u and v in ⁿℜ , we define
and
Note: These are our usual norm and distance in ⁿℜ . ⁿℜ is an inner product space with the dot product as its inner product.
ru =⟨
ru,
ru⟩
12 = (
ru⋅
ru) = u1
2 +u22 + ...+un
2 ,
d(ru,
rv)=
ru−
rv
=⟨ru−
rv,
ru−
rv⟩
12 = (
ru−
rv)⋅(
ru−
rv)
= (u1 −v1)2 + (u2 −v2 )
2 + ... + (un −vn)2 .
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8Rev.F09
How to Find an Inner Product, Norm, and Distance for Vectors in ⁿℜ ? (Cont.)
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Example 1: Let u = (1,2,-1) and v = (2,0,1) in ³. Find the ℜinner product, norms, and distance.
⟨ru,
rv⟩=
ru ⋅
rv = u1v1 + u2v2 + u3v3 = (1)(2) + (2)(0) + (−1)(1) = 1,
ru = ⟨
ru,
ru⟩
12 = u1
2 + u22 + u3
2 = 12 + 22 + (−1)2 = 6,rv = ⟨
rv,
rv⟩
12 = v1
2 + v22 + v3
2 = 22 + 02 +12 = 5, and
d(ru,
rv) =
ru −
rv = ⟨
ru −
rv,
ru −
rv⟩
12
= (1− 2)2 + (2 − 0)2 + (−1−1)2 = 9 = 3.
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9Rev.F09
How to Find an Inner Product, Norm, and Distance for Vectors (Matrices) in M22?
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In M22, the vectors are 2 x 2 matrices. Thus, given two matrices U and V in M22, we define
U =u1 u2
u3 u4
⎡
⎣⎢⎢
⎤
⎦⎥⎥,V =
v1 v2v3 v4
⎡
⎣⎢⎢
⎤
⎦⎥⎥.
Recall: tr(A) = sum of the entries on the main diagonal of A.
⟨U,V⟩= tr(UTV ) = tr(V TU ) = ⟨V ,U⟩= u1v1 + u2v2 + u3v3 + u4v4 .
U =⟨U,U⟩12 = u12 +u2
2 +u32 +u4
2 , and
d(U,V) = U −V =⟨U −V,U −V⟩12 = ⟨U −V,U −V⟩
= (u1 −v1)2 + (u2 −v2 )
2 + (u3 −v3)2 + (u4 −v4 )
2 .
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10
Rev.F09
How to Find an Inner Product, Norm, and Distance for Vectors (Matrices) in M22? (Cont.)
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Example 2: Let
be matrices in the vector space M22. Find the inner product, norms and distance for U and V in M22.
U =u1 u2
u3 u4
⎡
⎣⎢⎢
⎤
⎦⎥⎥= 2 −1
3 1⎡
⎣⎢
⎤
⎦⎥,V =
v1 v2v3 v4
⎡
⎣⎢⎢
⎤
⎦⎥⎥= 0 9
4 6⎡
⎣⎢
⎤
⎦⎥
⟨U,V⟩= tr(UTV ) = tr(V TU ) = u1v1 + u2v2 + u3v3 + u4v4
= (2)(0) + (3)(4) + (−1)(9) + (1)(6) = 9.Recall: tr(A) = sum of the entries on the main diagonal of A.
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11
Rev.F09
How to Find an Inner Product, Norm, and Distance for Vectors (Matrices) in M22? (Cont.)
http://faculty.valenciacc.edu/ashaw/ Click link to download other modules.
U =⟨U,U⟩12 = u12 +u2
2 +u32 +u4
2 = 22 + (−1)2 + 32 +12 = 15,
V =⟨V,V⟩12 = u12 +u2
2 +u32 +u4
2 = 02 + 92 + 42 + 62 = 133, and
d(U,V) = U −V =⟨U −V,U −V⟩12 = ⟨U −V,U −V⟩
= (u1 −v1)2 + (u2 −v2 )
2 + (u3 −v3)2 + (u4 −v4 )
2
= (2 −0)2 + ((−1)−9)2 + (3−4)2 + (1−6)2
= 4 +100 +1+ 25 = 130.
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12
Rev.F09
How to Find an Inner Product, Norm, and Distance for Vectors (Polynomials) in P2?
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Let P2 be the set of all polynomials of degree less than or equal to two. For two polynomials
we define
p(x)=a0x0 + a1x
1 + a2x2 ,
q(x) =b0x0 +b1x
1 +b2x2
rp,
rq ∈P2 ,
⟨rp,
rq⟩= a0b0 + a1b1 + a2b2 ,
rp = ⟨
rp,
rp⟩
12 = a2
0 + a21 + a2
2 , and
d(rp,
rq) =
rp −
rq = ⟨
rp −
rq,
rp −
rq⟩
12
= (a0 − b0 )2 + (a1 − b1)12 + (a3 − b3)
2 .
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13
Rev.F09
How to Find an Inner Product, Norm, and Distance for Vectors (Polynomials) in P2? (Cont.)
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Example 3: Find the inner product, norms, and distance for p and q in P2, where
⟨rp,
rq⟩= a0b0 + a1b1 + a2b2 = (8)(1) + (−3)(−2) + (5)(7) = 8 + 6 + 35 = 49,
rp = ⟨
rp,
rp⟩
12 = a0
2 + a21 + a2
2 = 82 + (−3)2 + 52 = 98 = 7 2,
rq = ⟨
rq,
rq⟩
12 = b0
2 + b12 + b2
2 = 12 + (−2)2 + 72 = 54 = 3 6, and
d(rp,
rq) =
rp −
rq = ⟨
rp −
rq,
rp −
rq⟩
12 = (a0 − b0 )2 + (a1 − b1)1
2 + (a3 − b3)2
= (8 −1)2 + ((−3) − (−2))2 + (5 − 7)2 = 49 +1+ 4 = 54 = 3 6.
p(x)=8−3x+ 5x2 and q(x) =1−2x+ 7x2 .
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14
Rev.F09
How to Find an Inner Product, Norm, and Distance for Vectors (Functions) in C[a,b]?
http://faculty.valenciacc.edu/ashaw/ Click link to download other modules.
⟨rf ,
rg⟩= f (x)g(x)dx
a
b
∫ ,
rf = ⟨
rf ,
rf ⟩
12 = [ f (x)]2 dx
a
b
∫⎛
⎝⎜⎞
⎠⎟
12
= f 2 (x)dxa
b
∫ ,
and d(rf ,
rg) =
rf −
rg = ⟨
rf −
rg,
rf −
rg⟩
12 = [ f (x) − g(x)]2 dx
a
b
∫⎛
⎝⎜⎞
⎠⎟
12
.
Let C[a,b] be the set of all continuous functions on [a,b].
For all f and g in C[a,b], we define
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15
Rev.F09
How to Find an Inner Product, Norm, and Distance for Vectors (Functions) in C[a,b]? (Cont.)
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Example 4: Let f = f(x) = 1 and g = g(x) = -x. Find the inner product, norms, and distance on C[2,4].
⟨rf ,
rg⟩= f (x)g(x)dx
2
4
∫ = (1)(−x)dx2
4
∫ = −x2
22
4
= (−8) − (−2) = −6,
rf = ⟨
rf ,
rf ⟩
12 = [ f (x)]2 dx
2
4
∫⎛
⎝⎜⎞
⎠⎟
12
= f 2 (x)dx2
4
∫ = dx2
4
∫ == x2
4= 2,
rg = ⟨
rg,
rg⟩
12 = [g(x)]2 dx
2
4
∫⎛
⎝⎜⎞
⎠⎟
12
= g2 (x)dx2
4
∫ = (−x)2 dx2
4
∫ ==x3
32
4
= 214
3,
and d(rf ,
rg) =
rf −
rg = ⟨
rf −
rg,
rf −
rg⟩
12 = [ f (x) − g(x)]2 dx
2
4
∫⎛
⎝⎜⎞
⎠⎟
12
= (1+ x)2 dx2
4
∫ = (1+ 2x + x2 )dx2
4
∫ = (x + x2 +x3
3)
2
4
= 72
3.
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16
Rev.F09
The Cauchy-Schwarz Inequality
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Cauchy-Schwarz Inequality:
for all f, g in an inner product space V, with the norm induced by
the inner product. We evaluate the Cauchy-Schwarz inequality
for the previous examples.
⟨rf ,
rg⟩ ≤
rf
rg
1. ⟨ru,
rv⟩ =1≤ 6 5 =
ru
rv from Example 1.
2 ⟨U,V⟩ =9 ≤ 15 133 = U V from Example 2.
3. ⟨rp,
rq⟩ =49 ≤(7 2)(3 6) =
rp
rq from Example 3.
4. ⟨rf ,
rg⟩ =6 ≤( 2)(2
143) =
rf
rg from Example 4.
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17
Rev.F09
Orthogonality for Vectors (Functions) in C[a,b]
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Example 5: Let f = f(x) = 1 and g = g(x) = ex. Find the inner
product on C[0,2].
Since the inner product is not zero, f and g are not orthogonal
functions in C[0,2].
Example 6: Let f = f(x) = 5 and g = g(x) = cos(x). Find the
inner product on C[0,π].
Since the inner product is zero, f and g are orthogonal functions
in C[0,π].
⟨rf ,
rg⟩= f (x)g(x)dx
0
2
∫ = (1)(ex )dx0
2
∫ = e2 − e0 = e2 −1 ≠ 0
⟨rf ,
rg⟩= f (x)g(x)dx
0
π
∫ = 5cos(x)dx0
π
∫ == 5 cos(x)dx0
π
∫= 5[sin(π ) − sin(0)] = 5[0 − 0] = 0
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18
Rev.F09
Orthogonality for Vectors (Functions) in C[a,b] (Cont.)
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Example 7: Let f = f(x) = 4x and g = g(x) = x2. Find the inner product on C[-1,1].
Since the inner product is zero, f and g are orthogonal functions in C[-1,1].
⟨rf ,
rg⟩= f (x)g(x)dx
−1
1
∫ = (4x)(x2 )dx−1
1
∫ == 4 x3 dx−1
1
∫ = x4( )−1
1= 1−1 = 0
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19
Rev.F09
Inner Product and Orthogonality for Vectors (Functions) in C[a,b] (Cont.)
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Example 8: Let f = f(x) = 1 and g = g(x) = sin(2x). Find the inner product on C[-π,π].
Since the inner product is zero, f and g are orthogonal functions in C[-π,π].
⟨rf ,
rg⟩= f (x)g(x)dx
−π
π
∫ = (1)(sin(2x))dx−π
π
∫ = sin(2x)dx−π
π
∫ = −1
2cos(2x)
−π
π
= −1
2cos(2π )⎡
⎣⎢⎤⎦⎥
− −1
2cos(−2π )⎡
⎣⎢⎤⎦⎥
= −1
2cos(2π ) +
1
2cos(2π ) = 0,
cos(2x) is even.
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20
Rev.F09
The Generalized Theorem of Pythogoras
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Generalized Theorem of Pythogoras: If f and g are orthogonal vectors in an inner product space V, then
Proof: Let f and g be orthogonal in V, then
Thus,rf +
rg
2=⟨
rf +
rg,
rf +
rg⟩ =⟨
rf ,
rf +
rg⟩ + ⟨
rg,
rf +
rg⟩
=⟨rf ,
rf ⟩ + ⟨
rf ,
rg⟩ + ⟨
rg,
rf ⟩ + ⟨
rg,
rg⟩
=rf
2+ 2⟨
rf ,
rg⟩ +
rg 2
=rf
2+
rg 2 .
⟨rf ,
rg⟩= 0.
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21
Rev.F09
The Generalized Theorem of Pythogoras (Cont.)
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The Generalized Theorem of Pythogoras
We evaluate the theorem for the previous examples. From example 6, we have
rf +
rg
2= [5 + cos(x)]2 dx
0
π
∫ = (25 + (2)(5)cos(x) + cos2 (x))dx0
π
∫
= 25dx0
π
∫ + 2 (5)cos(x)dx0
π
∫ + cos2 (x)dx0
π
∫
=rf
2+ 2⟨5,cos(x)⟩ +
rg 2 =
rf
2+ 2(0) +
rg 2 =
rf
2+
rg 2 .
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22
Rev.F09
The Generalized Theorem of Pythogoras (Cont.)
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From Example 7, we have
Notice that we have used orthogonality to obtain our results without directly computing the integrals.
Next, we will compute the integrals directly to obtain the result.
rf +
rg
2= [4x+ x2 ]2 dx
−1
1
∫ = (16x2 + (2)(4x)x2 + x4 )dx−1
1
∫
= 16x2 dx−1
1
∫ + 2 4x3 dx−1
1
∫ + x4 dx−1
1
∫
=rf
2+ 2⟨4x,x2 ⟩ +
rg 2 =
rf
2+ 2(0) +
rg 2 =
rf
2+
rg 2 .
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23
Rev.F09
The Generalized Theorem of Pythogoras (Cont.)
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Thus,
rf
2=⟨
rf ,
rf ⟩ = f 2 (x)dx
−1
1
∫ = [ f (x)]2 dx−1
1
∫ = (4x)(4x)dx−1
1
∫ ==16 x2 dx−1
1
∫ =(16)x3
3−1
1
=323
rg 2 =⟨
rg,
rg⟩ = g2 (x)dx
−1
1
∫ = [g(x)]2 dx−1
1
∫ = (x2 )(x2 )dx−1
1
∫ == x4 dx−1
1
∫ =x5
5−1
1
=25
rf +
rg
2=⟨
rf +
rg,
rf +
rg⟩ = [ f (x) + g(x)]2 dx
−1
1
∫ = (4x+ x2 )(4x+ x2 )dx−1
1
∫
= (16x2 + 8x3 + x4 )dx−1
1
∫ =16x3
3+8x4
4+
x5
5⎛
⎝⎜⎞
⎠⎟−1
1
=16615
=323+25=
rf
2+
rg 2 .
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24
Rev.F09
How to Find the Cosine of the Angle Between Two Vectors in an Inner Product Space?
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Example 9: Let ⁵ have the Euclidean inner product. ℜ
Find the cosine of the angle between
u = (2,1,0,-1,5) and v = (1,-1,-2,3,1).
cos(θ) =⟨ru,
rv⟩
ru
rv=
u1v1 +u2v2 +u3v3 + .u4v4 + +u5v5u12 +u2
2 +u32 +u4
2 +u52 v1
2 + v22 + v3
2 + v42 + v5
2
=(2)(1) + (1)(−1) + (0)(−2) + (−1)(3) + (5)(1)
22 +12 + 0 + (−1)2 + 52 12 + (−1)2 + (−2)2 + (3)2 +12
=3
4 31.
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25
Rev.F09
How to Find the Cosine of the Angle Between Two Vectors in an Inner Product Space? (Cont.)
http://faculty.valenciacc.edu/ashaw/ Click link to download other modules.
Example 10: Let P2 have the previous inner product.
Find the cosine of the angle between p and q.
cos(θ) =⟨rp,
rq⟩
rp
rq=
a0b0 + a1b1 + a2b2a02 + a1
2 + a22 b0
2 +b12 +b2
2
=(2)(−2) + (6)(−1) + (3)(4)
22 + 62 + 32 (−2)2 + (−1)2 + (4)2
=2
7 21.
rp =p(x) =a0x
0 + a1x1 + a2x
2 =2 + 6x+ 3x2 ,rq=q(x) =b0x
0 +b1x1 +b2x
2 =−2−x+ 4x2
![Page 26: 1 MAC 2103 Module 10 lnner Product Spaces I. 2 Rev.F09 Learning Objectives Upon completing this module, you should be able to: 1. Define and find the](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dc95503460f94abebee/html5/thumbnails/26.jpg)
26
Rev.F09
Quick Review on a Basis for a Vector Space and the Dimension of a Vector Space
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Let be nonzero vectors in V. Then for , we have that
W = span(S) = {all linear combinations of } is a subspace of V.
If S contains some linearly dependent vectors, then the dim(W) < n.
If S is a linearly independent set of vectors, then S is a basis for the vector space W. W is a proper subspace of V, if dim(W) < dim(V). If dim(W) = dim(V) = n, then S is a basis for V.
A non-trivial vector space V always have two subspaces:
the trivial vector space, {0} and V.
rv1,
rv2 ,...,
rvn
S ={rv1,
rv2 ,...,
rvn}
rv1,
rv2 ,...,
rvn
![Page 27: 1 MAC 2103 Module 10 lnner Product Spaces I. 2 Rev.F09 Learning Objectives Upon completing this module, you should be able to: 1. Define and find the](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dc95503460f94abebee/html5/thumbnails/27.jpg)
27
Rev.F09
Quick Review on a Basis for a Vector Space and the Dimension of a Vector Space
http://faculty.valenciacc.edu/ashaw/ Click link to download other modules.
So, we need two conditions for the set S to be a basis of a vector space, it must be a linearly independent set and it must span the vector space. The number of basis vectors in S is the dimension of the vector space.
For example: dim( ²ℜ )=2, dim( ³ℜ )=3, dim( ⁵ℜ )=5,
dim (P2)=3, dim(M22)=4, and dim(C[a,b]) is infinite.
![Page 28: 1 MAC 2103 Module 10 lnner Product Spaces I. 2 Rev.F09 Learning Objectives Upon completing this module, you should be able to: 1. Define and find the](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dc95503460f94abebee/html5/thumbnails/28.jpg)
28
Rev.F09
Rank, Row Rank, and Column Rank of a Matrix
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The dimensions of the row space of A, column space of A, and nullspace of A are also called the row rank of A, column rank of A, and nullity of A, respectively.
The rank of A = the row rank of A = the column rank of A, and is the number of linearly independent columns in the matrix A.
The nullity of A = dim(null(A)) and is the number of free variables in the solution space.
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29
Rev.F09
The Orthogonal Complement of a Subspace W
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The orthogonal complement of W, is the set of all vectors in a finite dimensional inner product space V that are orthogonal to every vector in W.
Both W and are subspaces of V where
dim(W) + dim( ) = dim(V).
The only vector common to W and is 0, and W ⊥
W ⊥
W ⊥W ⊥
W =(W⊥ )⊥ .
![Page 30: 1 MAC 2103 Module 10 lnner Product Spaces I. 2 Rev.F09 Learning Objectives Upon completing this module, you should be able to: 1. Define and find the](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dc95503460f94abebee/html5/thumbnails/30.jpg)
30
Rev.F09
The Four Fundamental Matrix Spaces
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Let A be an m x n matrix, then:
1.The null(A) and the row(A) are orthogonal complements in ⁿ with respect to the Euclidean inner product. ℜ
2.The null(AT) and the col(A) are orthogonal complements in ℜᵐ with respect to the Euclidean inner product.
Note that row(A) = col(AT) and col(A) = row(AT).
The four fundamental matrix spaces are:
• row(A) = col(AT),
• col(A) = row(AT),
• null(A), and
• null(AT).
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31
Rev.F09
How to Find a Basis for the Orthogonal Complement of the Subspace of ⁿℜ Spanned by the Vectors?
http://faculty.valenciacc.edu/ashaw/ Click link to download other modules.
Example 11: Find a basis for the orthogonal complement of the subspace of ⁿℜ spanned by the vectors v1, v2, and v3.
Let V = span({v1, v2, v3}). Then, V is a subspace of of ⁿℜ if v1, v2, v3 ∈ ⁿℜ . Let
From the last module, we know that the null(A) is the orthogonal complement to the row(A) = col(AT), and that the null(A) is the solution space of the homogeneous system, Ax = 0. Let v1, v2, v3 be the row vectors of the matrix A. Then, row(A) is the orthogonal complement to null(A) which is the solution space to Ax = 0. We shall use Gauss Elimination to reduce A to a row echelon form to find the basis for null(A).
rv1 =(1,−1,3),
rv2 =(5,−4,−4),
rv3 =(7,−6,2).
![Page 32: 1 MAC 2103 Module 10 lnner Product Spaces I. 2 Rev.F09 Learning Objectives Upon completing this module, you should be able to: 1. Define and find the](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dc95503460f94abebee/html5/thumbnails/32.jpg)
32
Rev.F09
How to Find a Basis for the Orthogonal Complement of the Subspace of ⁿℜ Spanned by the Vectors? (Cont.)
http://faculty.valenciacc.edu/ashaw/ Click link to download other modules.
r1r2r3
157
−1−4−6
3−42
⎡
⎣
⎢⎢⎢
⎤
⎦
⎥⎥⎥
=A
r1−5r1+ r2−7r1+ r3
100
−111
3−19−19
⎡
⎣
⎢⎢⎢
⎤
⎦
⎥⎥⎥
r1r2
−r2 + r3
100
−110
3−190
⎡
⎣
⎢⎢⎢
⎤
⎦
⎥⎥⎥
Since the null(A) is the solution space of the homogeneous system, Ax = 0, the general solution of the system is:
x3 =s,x2 −19x3 =0,x2 −19s=0,x2 =19s.x1 −x2 + 3x3 =0,x1 −19s+ 3s=0,x1 =16s.
Note that column 1 and column 2, with the red leading 1’s, are linearly independent. The corresponding columns of A form a basis for the col(A). Then, dim(col(A)) = 2.
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33
Rev.F09
How to Find a Basis for the Orthogonal Complement of the Subspace of ⁿℜ Spanned by the Vectors? (Cont.)
http://faculty.valenciacc.edu/ashaw/ Click link to download other modules.
The nonzero rows with the leading 1’s are linearly independent. These rows form a basis for row(A). Then, dim(row(A)) = 2.
Note that the row space and column space are both two dimensional, so rank(A) = 2. The rank(A) is the common dimension of the row space of A and the column space of A.
So, rank(A) = rowrank(A) = colrank(A) = dim(col(A)) =dim(row(A)) is always true for any m x n matrix A.
![Page 34: 1 MAC 2103 Module 10 lnner Product Spaces I. 2 Rev.F09 Learning Objectives Upon completing this module, you should be able to: 1. Define and find the](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dc95503460f94abebee/html5/thumbnails/34.jpg)
34
Rev.F09
How to Find a Basis for the Orthogonal Complement of the Subspace of ⁿℜ Spanned by the Vectors? (Cont.)
http://faculty.valenciacc.edu/ashaw/ Click link to download other modules.
Thus, the solution vector is:
and the vector
{w1} forms a basis for the null(A). In other words, {w1} = {(16,19,1)} forms a basis for the orthogonal complement of row(A).
x1
x2
x3
⎡
⎣
⎢⎢⎢
⎤
⎦
⎥⎥⎥=
16s19ss
⎡
⎣
⎢⎢⎢
⎤
⎦
⎥⎥⎥
=s16191
⎡
⎣
⎢⎢⎢
⎤
⎦
⎥⎥⎥
rw1 =
16191
⎡
⎣
⎢⎢⎢
⎤
⎦
⎥⎥⎥
![Page 35: 1 MAC 2103 Module 10 lnner Product Spaces I. 2 Rev.F09 Learning Objectives Upon completing this module, you should be able to: 1. Define and find the](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dc95503460f94abebee/html5/thumbnails/35.jpg)
35
Rev.F09
How to Find a Basis for the Orthogonal Complement of the Subspace of ⁿℜ Spanned by the Vectors? (Cont.)
http://faculty.valenciacc.edu/ashaw/ Click link to download other modules.
Since B = {w1} is a basis for null(A), span(B) = null(A), and
dim(null(A)) = 1 is the nullity of A. In this example, rank(A) is 2 and the nullity of A is 1, and the number of columns of A is 3.
For any m x n matrix A, rank(A) + nullity(A) is n, which is the number of columns of A.
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36
Rev.F09
Let’s Review Some Equivalent Statements
If A is an n x n matrix, and if TA: ⁿ→ ⁿ is multiplication by A, ℜ ℜthan the following are equivalent. (See Theorem 6.2.7)
• A is invertible.• Ax = 0 has only the trivial solution • The reduced row-echelon form of A is In.• A is expressible as a product of elementary matrices. • Ax = b is consistent for every n x 1 matrix b. • Ax = b has exactly one solution for every n x 1 matrix b. • det(A) ≠ 0.• The range of TA is ⁿℜ .• TA is one-to-one.
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![Page 37: 1 MAC 2103 Module 10 lnner Product Spaces I. 2 Rev.F09 Learning Objectives Upon completing this module, you should be able to: 1. Define and find the](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dc95503460f94abebee/html5/thumbnails/37.jpg)
37
Rev.F09
Let’s Review Some Equivalent Statements (Cont.)
• The column vectors of A are linearly independent.• The row vectors of A are linearly independent.• The column vectors of A span ⁿℜ . • The row vectors of A span ⁿℜ . • The column vectors of A form a basis for ⁿℜ . • The row vectors of A form a basis for ⁿℜ .• A has rank n = row rank n = column rank n = dim(col(A)).• A has nullity 0 = dim(null(A)).• The orthogonal complement of the nullspace of A,
null(A), is ⁿℜ .• The orthogonal complement of the row space of A,
row(A), is {0}.
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![Page 38: 1 MAC 2103 Module 10 lnner Product Spaces I. 2 Rev.F09 Learning Objectives Upon completing this module, you should be able to: 1. Define and find the](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dc95503460f94abebee/html5/thumbnails/38.jpg)
38
Rev.F09
What have we learned?We have learned to:
1. Define and find the inner product, norm and distance in a given inner product space.
2. Find the cosine of the angle between two vectors and determine if the vectors are orthogonal in an inner product space.
3. Find the orthogonal complement of a subspace of an inner product space.
4. Find a basis for the orthogonal complement of a subspace of ⁿ ℜspanned by a set of row vectors.
5. Identify the four fundamental matrix spaces of an m x n matrix A, and know the column rank of A, the row rank of A, and the rank of A.
6. Know the equivalent statements of an n x n matrix A.
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![Page 39: 1 MAC 2103 Module 10 lnner Product Spaces I. 2 Rev.F09 Learning Objectives Upon completing this module, you should be able to: 1. Define and find the](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dc95503460f94abebee/html5/thumbnails/39.jpg)
39
Rev.F09
Credit
Some of these slides have been adapted/modified in part/whole from the following textbook:
• Anton, Howard: Elementary Linear Algebra with Applications, 9th Edition
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