 Hello and welcome to the session. In this session first we will discuss congruence of plane figures. Congruent objects are exact copies of one another. Then we have relation of two objects being congruent is called congruence. Then the method of superposition exam is the congruence of plane figures. Let's consider the plane figures F1 and F2 if the trace copy of the plane figure F1 fits exactly on that of the plane figure F2 then we say the two plane figures F1 and F2 are congruent and we write it as F1 congruent to F2. Next we discuss congruent among line segments. Consider the two line segments AB and CD. We may write this as line segment AB and line segment CD. Now if the length of the line segment AB is equal to the length of the line segment CD then we say the line segment AB is congruent to the line segment CD. And in case if we have that the line segment AB is congruent to the line segment CD then we say the length of the line segment AB is equal to length of the line segment CD. Next is congruence of angles. Consider the angles angle AVC and angle PQR. If we have that the measure of angle AVC is equal to the measure of angle PQR then we say angle ABC is congruent to angle PQR and in case if we have that angle ABC is congruent to angle PQR then measure of angle ABC is equal to measure of angle PQR. Next we have congruence of triangles. We already have discussed that two line segments and two angles are congruent if they are exact copy of each other. Similarly we say that two triangles are congruent if they are copies of each other and when superposed they cover each other exactly. Consider the triangle ABC and triangle PQR. Now these two triangles have same shape and same size so we say triangle ABC and triangle PQR are congruent and we will write it as triangle ABC is congruent to triangle PQR. We should remember one thing that while we talk about the congruence of two triangles then the measure of angles lens of size and matching of vertices matters. Now first let's consider the corresponding vertices in both these triangles. These are given by A and P then B and Q then C and now let's see the corresponding sides in both these triangles. These are given as AB and PQ then BC and QR then AC and PR. Now let's discuss the corresponding angles these are given as angle A and angle P then angle B and angle Q, angle C and angle R. Now in this case the correspondence that we take is A corresponds to P, B corresponds to Q and C corresponds to R we may also write this as ABC corresponds to PQR. Now under this correspondence we see that the two triangles triangle ABC and triangle PQR are congruent then we say the corresponding parts which include the angles and the sides of the two triangles are equal. So this completes the session hope you have understood the concept of congruence of plane figures, congruence of line segments, congruence of angles and congruence of triangles.