 Welcome to the session I am Deepika here. Let's discuss a question which says in given figure a quadrilateral abcd is drawn to circumscribe a circle note that ab plus cd is equal to ab plus bc. Now we know that a tangent to a circle is a line that intersects the circle at only one point. So let's start the solution. This figure a quadrilateral abcd is drawn to circumscribe a circle. We have four external points abc and b from which tangents are drawn to the circle. Since the lengths of the tangents from an external point to a circle are equal therefore the lengths of two tangents ab and as which are drawn from a are equal that is ab is equal to as let us give this as number one. Similarly lengths of two tangents drawn from b which are bp and bq are equal let us give this as number two. Again two tangents drawn from cr, cr is cq so their lengths are also equal r is equal to cq let us give this as number three. Again the lengths of two tangents drawn from ds and dr so their lengths are also equal so we have dr is equal to ds let us give this as number four. On adding one two three and four we get ap plus bp plus cr plus dr is equal to as plus bq plus cq plus ds. Now ap plus bp is ab plus dr is cd this is equal to now as ds is ab bq plus cq is bc. Hence we have proved the required result that is ab plus cd is equal to ab plus bc. I hope the solution is clear to you why we check here.