 Welcome to your session. Let us discuss the following question. The question says proof that the sum of either pair of opposite angles of a cyclic-coordination is 180 degree. Using the above to the following, in figure 3, A, B, C, D is a cyclic-coordination in which angle A is equal to x plus y plus 10 degree, angle B is equal to y plus 2 degree, angle C is equal to x plus y minus 30 degree and angle D is equal to x plus y degree, find x and y. Let us now begin with the solution. We are given a cyclic-coordination A, B, C, D equal to 180 degree and angle B plus angle D is equal to 180 degree. I mean construction O, B and O is equal to half of reflex and equation of a mark. Angle B, C, D is equal to 180 degree. Let us now move on to the second part, x plus y is equal to equation of a mark. Again, in cyclic-coordination A, B, C, D, angle B plus angle D is equal to 180 degree, angle B is equal to y plus 20 is equal to x plus y to 160. Let us name this as equation number 2. Now we will solve 1 and 2 and we have x plus y equals to 100 and from 2 we have x plus 2 y equals to 160. Let us now subtract these equations. They are minus y equals to minus 60. This implies y is equal to 60. Now x plus y is equal to 100 and y is equal to 60 degree. This implies x is equal to 40 degree. x equals to 40 degree and y equals to 60 degree is a required answer. This completes the session. Bye and take care.