2, the center of gravity of the triangle, the center of gravity of the triangle is the intersection of the three center lines of the triangle. When the geometry is uniform, the center of gravity coincides with the centroid. The center of gravity is the intersection of three sides of a triangle, and the intersection of three lines can be proved by dovetail theorem. The center of gravity of other figures, the following geometry is uniform, line segments refer to thin rods, and plane figures refer to thin plates. The center of gravity of a triangle is the intersection of three sides. The center of gravity of the line segment is the midpoint of the line segment.