HG 46
D25. The areas of triangles are proportional to the defect numbers of the triangles, the constant of proportionality being the same for all triangles. Thus, the area A of a triangle is proportional to its defect d, A = k d, where k is any positive constant.
T75. Two triangles have the same area if and only if they have the same angle sum.
T76. The area of triangle ABC is equal to the sum of the areas of the triangles resulting from any subdivision of the triangle ABC into triangles.