Answer
True
Work Step by Step
A surface $f(x, y)=z$ has a saddle point at $\left(x_{0}, y_{0}\right)$ if there are two distinct vertical planes through this point such that the trace of the surface in one of the planes has a relative maximum at $\left(x_{0}, y_{0}\right)$ and the trace in the other has a relative minimum at $\left(x_{0}, y_{0}\right)$
