RS Aggarwal Solutions for Class 9 Chapter 9 “Congruence of triangles and inequalities in a triangle” is described, if two sides and an angle of one triangle are equal to two sides and an angle of another triangle, then the two triangles must be congruent. Congruence is the term used to define an object and its mirror image. Two objects or shapes are said to be congruent if they superimpose on each other. Their shape and dimensions are the same. In the case of geometric figures, line segments with the same length are congruent, and angle with the same measure are congruent. Two triangles are said to be congruent if all their three sides and three angles are equal. But it is necessary to find all six dimensions. Hence, the congruence of triangles can be evaluated by knowing only three values out of six. Some of the concepts which are explained in this chapter are SAS, ASA, AAS, SSS and RHS congruence criterion and inequalities in a triangle along with theorems.