
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
Given lines l<sub>1</sub>: ax + y + 2 = 0 and l<sub>2</sub>: x + y = 0, find the value of 'a' such that l<sub>1</sub> is perpendicular to l<sub>2</sub>.

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