RD Sharma Solutions for Class 7 Chapter 15 “Properties of Triangles”. A triangle is a polygon with three edges and three vertices. A triangle with vertices A, B, and C is denoted. In this chapter, we will learn about a plane figure formed by three non-parallel line segments. It also deals with interior and exterior of the triangle, types of triangles based on lengths and sides, types of triangles based on their measures of angles, the perimeter of triangles, angle sum property of triangles, exterior and interior opposite angles of a triangle, triangular inequality property, Pythagoras theorem, the converse of Pythagoras theorem and Pythagorean triplets.