 Hello friends welcome to the session I am Alka. Let's discuss triangles. Our given question is state which pair of triangles in figure 6.34 are similar. Write the similarity criteria used by you for answering that question and also write the pairs of similar triangles in symbolic form. So before starting with the solution let me tell you the different criteria of similarity of triangles. Our first criteria is A, A, A that is angle, angle, angle, criteria. Suppose we are given two triangles A, B, C, D, E, F. Now if in two triangles corresponding angles are equal then the corresponding sides are in the same ratio. Then we see that two triangles are similar by A, A, A criteria. So this can be written as angle A equal to angle D, angle B equal to angle E, angle C equal to and this implies A, B upon D, E equal to AC upon D, F equal to BC upon E, F. Therefore the two triangles A, B, C and triangle D, E, F are similar. Now we see the second criteria that is S, S, S criteria which is side, side, side criteria. Now suppose we are given two triangles, B, C, D, given two triangles, sides of one triangle are proportion to the sides of the other triangle. Then their corresponding angles are equal and the two triangles are similar. This can be written as A, B upon D, E equal to AC upon D, F equal to BC upon F. Therefore angle A equal to angle B, angle B equal to angle E, angle C equal to angle F. This implies triangle A, B, C is similar to triangle D, E, F by S, S, S criteria. Now we will see our third criteria which is S, A, S that is side, angle, side criteria. Suppose in the two given triangles B, C, D, E, if angle A is equal to angle D and AB upon D, E is equal to AC upon D, F then two triangles are similar by S, A, S criteria. So if angle A equal to angle D and AB upon D, E equal to AC upon D, F. This implies triangle A, B, C is similar to triangle D, E, F by S, A, S criteria. Here we can say 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 the two triangles are similar. So this was the key idea behind the question that contains three criteria A, A, A, S, S, S and S, A, S criteria. Now let us start with the solution. We are given two triangles A, B, C and P, Q, R. Angle A is 60, B is 80 and C is 40 degree, angle P is 60 degree, Q is 80 degree and R is 40 degree. Now in triangle A, B, C and triangle P, Q, R we observe that angle A equal to angle P equal to 60 degree, angle B equal to angle Q equal to 80 degree, angle C equal to angle R equal to 40 degree. Therefore by A, A, A criteria of similarity the two triangles are similar. Triangle A, B, C is similar to triangle D, E, F. Therefore they are similar by A, criteria similarity. Okay, this was the solution and I enjoyed the session. Goodbye and take care.