
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 line $l_1$ with parametric equations $ \begin{cases} x=-2t \\ y=2+kt \end{cases} $ (where $t$ is a parameter) and the line $l_2$ with parametric equations $ \begin{cases} x=2+s \\ y=1-2s \end{cases} $ (where $s$ is a parameter) are perpendicular to each other, find the value of the real number $k$.

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