We could do it dy dx. Or, maybe we will want to actually make a change of variables to first shift this to the origin, x-2 you know, change x to x minus two and then switch to polar coordinates.

也可以dy，dx来划分，或者,对变量做一下变化，移动到原点，就是把x变成,然后再转化成极坐标。

youdao

The syntax of a switch directive option is $ followed by the directive letter, followed by a plus (+) or a minus (-).

编译器指令的语法是“$”后紧跟一个指令字符，再跟一个“-”或“+”。

youdao