Question

高等数学多元微分学，画圈的地方怎么运算的？

Answer 1

把对应的M点处x y z 值带进去就行

一条竖直线段右下角有字母M，就是要你带进去求值

Answer 2

叉乘公式啊，列个行列式，第一行i,j,k，第二行和第三行分别是叉乘的两项，将M点的坐标代入就ok了，so easy (note: i, j and k represent the corresponding unit vector along the direction of axis x, y and z)
When you don't know how to solve a sophisticated problem, find out its definition and think it over until you can figure out the problem.

追问

没学行列式