 Hello and welcome to the session. In this session we will learn about the criteria for similarity of triangles. We know that two triangles are similar if their corresponding angles are equal and their corresponding sides are in the same ratio. So here we have six pairs of corresponding parts of triangles to prove that two triangles are similar. So in this section we will make an attempt to arrive at certain criteria for similarity of two triangles involving relationship between less number of pairs of corresponding parts of the two triangles instead of all the six pairs of corresponding parts. If in two triangles we have corresponding angles are equal then this implies that their corresponding sides in same ratio. And hence the two triangles are similar and this is called AAA that is angle, angle, angle criteria for similarity of two triangles. Like in this case if the corresponding angles are equal in the two triangles then we have that their corresponding sides are in the same ratio and so the two triangles are similar by AAA that is angle, angle, angle criteria for similarity of two triangles. Now if two angles of a triangle are respectively equal to two angles of another triangle then obviously by angles and property of triangle which says that the sum of the three angles of a triangle is 180 degree we get that the third angle of the triangles will be equal. And so AAA criteria for similarity of triangles can also be stated as if in two triangles two angles of one triangle are respectively equal to two angles of another triangle then we say that two triangles are similar. This may be referred to as AAA that is angle, angle criteria for similarity of two triangles. Now in the next criteria we have that if in two triangles sides of one triangle are proportional to the sides of the other triangle then their corresponding angles are equal and hence the two triangles would be similar this criteria is referred as SSS that is side, side, side criteria for similarity of two triangles. Like in these two triangles if the sides of one triangle are proportional to the sides of the other triangle then their corresponding angles are equal and hence the two triangles would be similar this is called the SSS criteria for similarity. Next criteria is that if one angle of a triangle is equal to one angle of the other triangle and the sides including these angles are proportional then we say that two triangles are similar and this criteria is referred to as SAS that is side, angle, side criteria. Like in these two triangles if one angle of one triangle is equal to the corresponding angle of the other triangle and the sides including these angles are proportional then we say that the two triangles are similar by SAS side, angle, side criteria. So these are the three criteria for similarity of triangles. This completes the session hope you have understood all the three criteria for similarity of triangles which would help you check the similarity of any two given triangles.