ベクトルの掛算
\begin{array}{lccl}
&\boldsymbol{A} &=& A_x e_x + A_y e_y + A_z e_z \\
&\boldsymbol{B} &=& B_x e_x + B_y e_y + B_z e_z \\
&|\boldsymbol{A}| &=& \sqrt{{A_x}^2 + {A_y}^2 + {A_z}^2} \\
\\
1. 整数倍:& k \boldsymbol{A} &=& k A_x e_x + k A_y e_y + k A_z e_z \\
\\
2. 内積:& \boldsymbol{A} \cdot \boldsymbol{B} &=& |\boldsymbol{A}||\boldsymbol{B}| cos \theta = A_xB_x + A_yB_y + A_zB_z \\
\\
3. 外積:& \boldsymbol{A} \times \boldsymbol{B} &=& |\boldsymbol{A}||\boldsymbol{B}| sin \theta = e_x(A_yB_z - A_zB_y) + e_y(A_zB_x - A_xB_z) + e_z(A_xB_y - A_yB_x) \\
\\
4. テンソル積:& \boldsymbol{A} \otimes \boldsymbol{B} &=& (A_x e_x + A_y e_y + A_z e_z) \otimes (B_x e_x + B_y e_y + B_z e_z) \\
& &=&e_x \otimes e_xA_xB_x + e_x \otimes e_y A_xB_y + e_x \otimes e_zA_xB_z\\
& & &e_y \otimes e_xA_yB_x + e_y \otimes e_y A_yB_y + e_y \otimes e_zA_yB_z\\
& & &e_z \otimes e_xA_zB_x + e_z \otimes e_y A_zB_y + e_z \otimes e_zA_zB_z\\
\end{array}