
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 the polar coordinate system, given point A (2, $\frac{\pi}{2}$), and point B lying on the line $l: \rho \cos \theta + \rho \sin \theta = 0$ (where $0 \leq \theta \leq 2\pi$), find the polar coordinates of point B when the length of segment AB is the shortest.

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