1.向量

设 $\vec a=\lbrace a_x,a_y,a_z \rbrace , \vec b=\lbrace b_x,b_y,b_z\rbrace , \vec c=\lbrace c_x,c_y,c_z\rbrace$
向量运算
加减:$\vec a \pm \vec b=\lbrace a_x \pm b_x , a_y \pm b_y , a_z \pm b_z \rbrace$