1. Given that $O$ is a point inside $\triangle A B C$, and satisfies
$$
O A \cdot O B=O B \cdot O C=O C \cdot O A \text {. }
$$

Then point $O$ is the $\triangle A B C$'s $\qquad$ .
ニ、1. Orthocenter.
From $O A \cdot O B=O B \cdot O C$ we can get $O B \cdot A C=0$, so, point $O$ lies on the altitude of side $A C$. Similarly, we can prove that point $O$ also lies on the altitudes of the other sides. Therefore, point $O$ is the orthocenter of $\triangle A B C$.