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一阶行列式:
det
(
A
)
=
a
\det \left( A \right) = a
det(A)=a
二阶行列式:
det
(
A
)
=
a
11
a
22
−
a
12
a
21
\det \left( A \right) = {a_{11}}{a_{22}} - {a_{12}}{a_{21}}
det(A)=a11a22−a12a21
三阶行列式:
det
(
A
)
=
a
11
a
22
a
33
+
a
12
a
23
a
31
+
a
21
a
32
a
13
−
a
31
a
22
a
13
−
a
21
a
12
a
33
−
a
32
a
23
a
11
\det \left( A \right) = {a_{11}}{a_{22}}{a_{33}} + {a_{12}}{a_{23}}{a_{31}} + {a_{21}}{a_{32}}{a_{13}} - {a_{31}}{a_{22}}{a_{13}} - {a_{21}}{a_{12}}{a_{33}} - {a_{32}}{a_{23}}{a_{11}}
det(A)=a11a22a33+a12a23a31+a21a32a13−a31a22a13−a21a12a33−a32a23a11
高阶行列式:利用行列式展开法则求解,行列式等于它的任一行(列)的各元素与其代数余子式的乘积之和。注:代数余子式
A
i
j
=
(
−
1
)
i
+
j
det
(
M
i
j
)
{A_{ij}} = {\left( { - 1} \right)^{i + j}}\det \left( {{M_{ij}}} \right)
Aij=(−1)i+jdet(Mij),
M
i
j
M_{ij}
Mij为划掉
a
i
j
a_{ij}
aij所在行列所得的
(
n
−
1
)
\left( {n - 1} \right)
(n−1)阶方阵。
det
(
A
)
=
a
i
1
A
i
1
+
a
i
2
A
i
2
+
⋯
+
a
i
n
A
i
n
det
(
A
)
=
a
1
j
A
1
j
+
a
2
j
A
2
j
+
⋯
+
a
n
j
A
n
j
Matlab求解函数:
det
(
A
)
:返回方阵
A
的行列式
\det \left( A \right):返回方阵 A 的行列式
det(A):返回方阵A的行列式
性质1:矩阵与转置矩阵行列式相等。
性质2:互换行列式的两行(列),行列式变号。
性质3:行列式某行(列)的公因子可以提出去。
∣
a
11
a
12
⋯
a
1
n
⋮
⋮
⋮
k
a
i
1
k
a
i
2
⋯
k
a
i
n
⋮
⋮
⋮
a
n
1
a
n
2
⋯
a
n
n
∣
=
k
∣
a
11
a
12
⋯
a
1
n
⋮
⋮
⋮
a
i
1
a
i
2
⋯
a
i
n
⋮
⋮
⋮
a
n
1
a
n
2
⋯
a
n
n
∣
\left| {
性质4:如果行列式的某行(列)是两项之和,那么行列式等于两个行列式之和。
∣
a
11
a
12
⋯
a
1
n
⋮
⋮
⋮
a
i
1
+
a
i
1
′
a
i
2
+
a
i
2
′
⋯
a
i
n
+
a
′
i
n
⋮
⋮
⋮
a
n
1
a
n
2
⋯
a
n
n
∣
=
∣
a
11
a
12
⋯
a
1
n
⋮
⋮
⋮
a
i
1
a
i
2
⋯
a
i
n
⋮
⋮
⋮
a
n
1
a
n
2
⋯
a
n
n
∣
+
∣
a
11
a
12
⋯
a
1
n
⋮
⋮
⋮
a
i
1
′
a
i
2
′
⋯
a
i
n
′
⋮
⋮
⋮
a
n
1
a
n
2
⋯
a
n
n
∣
{\left| {
性质5:行列式某行(列)的倍数加到另一行(列),行列式不变。
∣
a
11
a
12
⋯
a
1
n
⋮
⋮
⋮
a
i
1
a
i
2
⋯
a
i
n
⋮
⋮
⋮
a
j
1
+
k
a
i
1
a
j
2
+
k
a
i
2
⋯
a
j
n
+
k
a
i
n
⋮
⋮
⋮
a
n
1
a
n
2
⋯
a
n
n
∣
=
∣
a
11
a
12
⋯
a
1
n
⋮
⋮
⋮
a
i
1
a
i
2
⋯
a
i
n
⋮
⋮
⋮
a
j
1
a
j
2
⋯
a
j
n
⋮
⋮
⋮
a
n
1
a
n
2
⋯
a
n
n
∣
\left| {
加法:
A
+
B
=
B
+
A
(
A
+
B
)
+
C
=
A
+
(
B
+
C
)
数乘:
(
α
β
)
A
=
α
(
β
A
)
(
α
+
β
)
A
=
α
A
+
β
A
乘法:满足结合律,不满足交换律。
A
B
≠
B
A
(
A
B
)
C
=
A
(
B
C
)
A
(
B
+
C
)
=
A
B
+
A
C
(
A
+
B
)
C
=
A
C
+
B
C
α
(
A
B
)
=
(
α
A
)
B
=
A
(
α
B
)
行列式:
∣
A
B
∣
=
∣
A
∣
∣
B
∣
|{A B}|=|{A}||{B}|
∣AB∣=∣A∣∣B∣
转置:矩阵
A
A
A的转置,记作
A
T
{A^T}
AT
(
A
T
)
T
=
A
(
A
+
B
)
T
=
A
T
+
B
T
(
A
B
)
T
=
B
T
A
T
∣
A
T
∣
=
∣
A
∣
共轭转置:矩阵
A
A
A的共轭转置,记作
A
H
{A^H}
AH
(
A
H
)
H
=
A
(
A
+
B
)
H
=
A
H
+
B
H
(
A
B
)
H
=
B
H
A
H
∣
A
H
∣
=
∣
A
∣
H
(
k
A
)
H
=
k
H
A
H
逆性质:
(
A
B
)
−
1
=
B
−
1
A
−
1
(
A
T
)
−
1
=
(
A
−
1
)
T
A
可逆
⇔
A
满秩
⇔
∣
A
∣
≠
0
⇔
A
为非奇异矩阵
偏导数1:标量对一维矩阵求偏导,
X
X
X为
(
n
×
1
)
\left( {n \times 1} \right)
(n×1)向量。
∂
A
1
×
n
X
X
=
A
T
∂
X
T
A
n
×
1
X
=
A
∂
X
T
A
n
×
n
X
X
=
A
X
+
A
T
X
∂
X
T
A
T
A
X
X
=
2
A
T
A
X
偏导数2:标量对二维矩阵求偏导,
X
X
X为
(
m
×
n
)
\left( {m \times n} \right)
(m×n)矩阵。
∂
A
1
×
m
X
B
n
×
1
X
=
A
T
B
T
⇔
∂
A
T
X
B
X
=
A
B
T
∂
A
1
×
n
X
T
B
m
×
1
X
=
B
A
⇔
∂
A
T
X
T
B
X
=
B
A
T
参考1:线性代数与空间解析几何(郑宝东)
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