
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 set $M = \{(x, y) | y = f(x)\}$, if for any $(x_1, y_1) \in M$, there exists $(x_2, y_2) \in M$ such that $x_1x_2 + y_1y_2 = 0$ holds true, then the set $M$ is referred to as a "perpendicular counterpart set." Consider the following four sets:  
① $M = \{(x, y) | y = \frac{1}{x}\}$;  
② $M = \{(x, y) | y = \log_2 x\}$;  
③ $M = \{(x, y) | y = e^x - 2\}$;  
④ $M = \{(x, y) | y = \sin x + 1\}$.

Among these, the sequences corresponding to the "perpendicular counterpart sets" are __________.

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