@@ -110,8 +110,8 @@ A_{11} & \cdots & A_{1n} \\ \vdots & \ddots & \vdots \\ A_{m1} & \cdots & A_{mn}
110110\e nd{bmatrix}$" } :
111111
112112 <Collapse label = " $$
113- \nabla_x (A x) = A^T
114- $$" >
113+ \nabla_x (A x) = A^T
114+ $$" >
115115
116116 $$
117117 \begin{split}
@@ -136,23 +136,23 @@ A_{11} & \cdots & A_{1m} \\ \vdots & \ddots & \vdots \\ A_{n1} & \cdots & A_{nm}
136136\e nd{bmatrix}$" } :
137137
138138 <Collapse label = " $$
139- \nabla_x (x^T A) = A
140- $$" >
141-
142- $$
143- \begin{split}
144- &\ \nabla_x (x^T A) = \nabla_x (x_1 A_1 + x_2 A_2 + \cdots + x_n A_n) \\
145- =&\ \nabla_x (x_1 [A_{11} \cdots A_{1m}] + x_2 [A_{21} \cdots A_{2m}] + \cdots + x_n [A_{n1} \cdots A_{nm}]) \\
146- =&\ \nabla_x (x_1 A_1 + x_2 A_2 + \cdots + x_n A_n) \\
147- =&\ \nabla_x (x_1 A_1) + \nabla_x (x_2 A_2) + \cdots + \nabla_x (x_n A_n) \\
148- =&\ \begin{bmatrix} \
149- \frac{\partial}{\partial x_1} (x_1 A_1) , \frac{\partial}{\partial x_2} (x_2 A_2) , \cdots , \frac{\partial}{\partial x_n} (x_n A_n)
150- \end{bmatrix} \\
151- =&\ \begin{bmatrix}
152- A_1 , A_2 , \cdots , A_n
153- \end{bmatrix} = A
154- \end{split}
155- $$
139+ \nabla_x (x^T A) = A
140+ $$" >
141+
142+ $$
143+ \begin{split}
144+ &\ \nabla_x (x^T A) = \nabla_x (x_1 A_1 + x_2 A_2 + \cdots + x_n A_n) \\
145+ =&\ \nabla_x (x_1 [A_{11} \cdots A_{1m}] + x_2 [A_{21} \cdots A_{2m}] + \cdots + x_n [A_{n1} \cdots A_{nm}]) \\
146+ =&\ \nabla_x (x_1 A_1 + x_2 A_2 + \cdots + x_n A_n) \\
147+ =&\ \nabla_x (x_1 A_1) + \nabla_x (x_2 A_2) + \cdots + \nabla_x (x_n A_n) \\
148+ =&\ \begin{bmatrix} \
149+ \frac{\partial}{\partial x_1} (x_1 A_1) , \frac{\partial}{\partial x_2} (x_2 A_2) , \cdots , \frac{\partial}{\partial x_n} (x_n A_n)
150+ \end{bmatrix} \\
151+ =&\ \begin{bmatrix}
152+ A_1 , A_2 , \cdots , A_n
153+ \end{bmatrix} = A
154+ \end{split}
155+ $$
156156
157157 </Collapse >
158158
@@ -164,20 +164,20 @@ A_{11} & \cdots & A_{1n} \\ \vdots & \ddots & \vdots \\ A_{n1} & \cdots & A_{nn}
164164\e nd{bmatrix}$" } :
165165
166166 <Collapse label = " $$
167- \nabla_x x^T A x = (A + A^T) x
168- $$" >
169-
170- $$
171- \begin{split}
172- &\ \nabla_x x^T A x = \nabla_x \sum_{i=1}^n \sum_{j=1}^n x_i A_{ij} x_j \\
173- =&\ \frac{\partial}{\partial x_k} \sum_{i=1}^n \sum_{j=1}^n x_i A_{ij} x_j + \frac{\partial}{\partial x_k} \sum_{i=1}^n \sum_{j=1}^n x_j A_{ji} x_i \\
174- =&\ \sum_{i=1}^n \sum_{j=1}^n A_{ij} x_j + \sum_{i=1}^n \sum_{j=1}^n A_{ji} x_i \\
175- =&\ \sum_{j=1}^n A_{kj} x_j + \sum_{i=1}^n A_{ik} x_i \text{($i, j = k$ 时,$A_{kj} x_j, A_{ik} x_i$ 分别存在一项 $A_{kk} x_k$)} \\
176- =&\ \sum_{i=1}^n (\sum_{j=1}^n A_{ij} x_j) \cdot e_i + \sum_{j=1}^n (\sum_{i=1}^n A_{ji} x_i) \cdot e_j \\
177- =&\ \sum_{i=1}^n (\mathbf{A} \mathbf{x})_i \cdot e_i + \sum_{j=1}^n (\mathbf{A^T} \mathbf{x})_j \cdot e_j \\ \
178- =&\ (A + A^T) x
179- \end{split}
180- $$
167+ \nabla_x x^T A x = (A + A^T) x
168+ $$" >
169+
170+ $$
171+ \begin{split}
172+ &\ \nabla_x x^T A x = \nabla_x \sum_{i=1}^n \sum_{j=1}^n x_i A_{ij} x_j \\
173+ =&\ \frac{\partial}{\partial x_k} \sum_{i=1}^n \sum_{j=1}^n x_i A_{ij} x_j + \frac{\partial}{\partial x_k} \sum_{i=1}^n \sum_{j=1}^n x_j A_{ji} x_i \\
174+ =&\ \sum_{i=1}^n \sum_{j=1}^n A_{ij} x_j + \sum_{i=1}^n \sum_{j=1}^n A_{ji} x_i \\
175+ =&\ \sum_{j=1}^n A_{kj} x_j + \sum_{i=1}^n A_{ik} x_i \text{($i, j = k$ 时,$A_{kj} x_j, A_{ik} x_i$ 分别存在一项 $A_{kk} x_k$)} \\
176+ =&\ \sum_{i=1}^n (\sum_{j=1}^n A_{ij} x_j) \cdot e_i + \sum_{j=1}^n (\sum_{i=1}^n A_{ji} x_i) \cdot e_j \\
177+ =&\ \sum_{i=1}^n (\mathbf{A} \mathbf{x})_i \cdot e_i + \sum_{j=1}^n (\mathbf{A^T} \mathbf{x})_j \cdot e_j \\ \
178+ =&\ (A + A^T) x
179+ \end{split}
180+ $$
181181
182182 </Collapse >
183183
@@ -196,16 +196,16 @@ A_{11} & \cdots & A_{1n} \\ \vdots & \ddots & \vdots \\ A_{n1} & \cdots & A_{nn}
196196\e nd{bmatrix}$" } :
197197
198198 <Collapse label = " $$
199- \nabla_x \|x\|_2^2 = \nabla_x (x^T x) = 2x
200- $$" >
201-
202- $$
203- \begin{split}
204- &\ \nabla_x \|x\|_2 = \nabla_x (\sqrt{x^T x}) ^ 2 \\
205- =&\ \nabla_x (x^T x) = \nabla_x (x_1^2 + x_2^2 + \cdots + x_n^2) \\
206- =&\ 2x
207- \end{split}
208- $$
199+ \nabla_x \|x\|_2^2 = \nabla_x (x^T x) = 2x
200+ $$" >
201+
202+ $$
203+ \begin{split}
204+ &\ \nabla_x \|x\|_2 = \nabla_x (\sqrt{x^T x}) ^ 2 \\
205+ =&\ \nabla_x (x^T x) = \nabla_x (x_1^2 + x_2^2 + \cdots + x_n^2) \\
206+ =&\ 2x
207+ \end{split}
208+ $$
209209
210210 </Collapse >
211211
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