x And, so if we want partial z over partial x, well, so one way is just to say that's going to be the coefficient of dx in here or just to write down the other way.
如果想知道∂z/∂,一种观点认为，它是这里dx前面的系数,或者从别的观点来看。
the general notation for vector dr-- y equals dx, x roof, plus dy, y roof, z plus dz, z roof.
总的向量dr的符号-,=dr向量x+dy向量，+dz向量。
Namely, let's say that you have a function maybe of three variables, x, y, z, df = fxdx+fydy +fzdz then you would write df equals f sub x dx plus f sub y dy plus f sub z dz.
即是说，如果你有一个,含自变量，x，y，z的函数，那么。
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