
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 circle $O: x^2+y^2=r^2(r>0)$, $A(x_1, y_1)$, $B(x_2, y_2)$ are two points on circle $O$, satisfying $x_1+y_1=x_2+y_2=3$, $x_1x_2+y_1y_2=-\frac{1}{2}r^2$, calculate the value of $r$.

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