Exterior center: the intersection of three perpendicular bisector, the acute triangle is inside the triangle, the obtuse triangle is outside the triangle, and the right triangle is at the midpoint of the hypotenuse. The vertical line passing through the center of the circle is the bisector of the edge. Similarly, the straight line connecting the center of a circle and the midpoint of an edge is perpendicular to the edge.

Inner heart: the intersection of three bisectors. The distance from the center of the circle to the three sides is equal.

Vertical center: the intersection of three heights. The acute triangle is inside the triangle, the obtuse triangle is outside the triangle, and the right triangle is at the right vertex.

Center: the intersection of three midlines. The distance from the point to the vertex is twice as long as the distance from the point to the midpoint of the opposite side.

PS: It's been useless for a long time. Please forgive me if I remember correctly! ! !