
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
In $\triangle ABC$, it is given that $a^2+c^2-b^2=mac$, where $m\in\mathbb{R}$.
(I) Determine whether $m$ can be equal to 3 and explain the reason.
(II) If $m=-1$, $b=2\sqrt{7}$, $c=4$, find $\sin A$.

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