 Hello and welcome to the session. Let us discuss the following question. It says, if a line intersects two concentric circles at the circles with same center, with center O at A, B, C and D, prove that AB is equal to CD. See whether, 10.25 given in the book. Let us now move on to the solution. We have to prove AB is equal to CD. To prove this, we do the following construction. You draw a perpendicular from O, the center to the line. Let us now start the proof. Now we have two circles with same center, that is the concentric circles. For the outer circle, you see that AM is equal to MD. This is because perpendicular from the center to the cord bisects the cord. Now again for the inner circle, AM is equal to MC because of the same reason that the perpendicular from the center to the cord bisects the cord. So BM is equal to MC. Let us call this as 1 and this as 2. Now subtract from 1. So we have M minus BM is equal to MD minus MC. M minus BM is AB minus M. So we have proved that AB is equal to CD. Solve for this session goodbye and take care.