Here they are related by the equation of a surface.

这里它们通过曲面方程相互联系着。

youdao

So, just to get you used to this idea, I'm going to draw a level surface of a function of three variables OK, so it's a surface given by the equation w of x, y, z equals some constant c.

为了令你们习惯于这个想法，我画一个三变量函数的等值面,这是一个平面,由函数w=c给出的。

youdao

z Maybe we don't know how to solve for z as a function of x and y, but our surface is given by some equation.

也许我们不知道如何直接用x，y表示，但是曲面是由某些方程给出的。

youdao