
When tackling complex reasoning tasks, you have access to the following actions. Use them as needed to progress through your thought process.

[ASSESS]

[ADVANCE]

[VERIFY]

[SIMPLIFY]

[SYNTHESIZE]

[PIVOT]

[OUTPUT]

You should strictly follow the format below:

[ACTION NAME]

# Your action step 1

# Your action step 2

# Your action step 3

...

Next action: [NEXT ACTION NAME]


system

Find the derivative of the scalar field \(u=f(x, y, z)\) at the point \(M_{0}(x_{0}, y_{0}, z_{0})\) of the line \(l\), given by the system of equations

$$
\left\{\begin{array}{l}
f(x, y, z)=a \quad(a=\text { const }) \\
\varphi(x, y, z)=0
\end{array}\right.
$$

in the direction of this line.

Present the answer in LaTex format: \boxed{Your answer}
user