
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 the function f(x) = -e^x - x, let l1 be the tangent line at any point on its graph. If there always exists a point on the graph of the function g(x) = ax + cos(x) such that the tangent line l2 at that point is perpendicular to l1, find the range of possible values for a.

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