
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
Among the following sets of functions, identify which pairs represent the same function.  
①$y=x$ and $y=\sqrt{x^{2}}$;  
②$y=x$ and $y=\frac{x^{2}}{x}$;  
③$y=x^2$ and $s=t^2$;  
④$y=\sqrt{x+1} \cdot \sqrt{x-1}$ and $y=\sqrt{x^{2}-1}$.

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