Eccentricity theorem: the perpendicular lines of three sides of a triangle intersect at one point. This point is called the outer center of the triangle.
The heart is the center of the inscribed circle, that is, the circle is tangent to all three sides. If the center is connected with the tangent point, the distance from the center to the three sides is equal, that is, the center is the intersection of the bisectors of the angles.
The epicenter is the center of the circumscribed circle, which means that all three vertices of the triangle are on the circumscribed circle, so the distance from the center to the three vertices is equal. So it is the intersection of perpendicular bisector on each side.