Well, if I have a gradient field, then if I try to compute this line integral, I know it will be the value of the function at the end point minus the value at the starting point.
如果有一个梯度场，然后想计算线积分，我知道积分值是,起点的函数值减去终点的函数值。
2
The minus sign (-) or plus sign (+) before each change corresponds with the file names directly above the line.
每个更改前的减号(-)或加号(+)与行上方的文件名一致。
3
So I'm looking at all points to satisfy 2 X minus Y equal 0. And I'm often... it's often good to start with which point on the horizontal line, on this horizontal line Y is 0.