 Hi and welcome to the session. I am Asha and I am going to help you with the following question that says in figure 6.17 Po2 is a line, ray OR is perpendicular to line PQ. OS is another ray, line between rays OP and OR proves that angle ROS is equal to half angle TOS minus angle POS. So let us begin with the solution and we are given that ray OR is perpendicular to line PQ. So this implies angle PoR is equal to angle ROQ is equal to 90 degree. We have to prove angle ROS is equal to half angle TOS minus angle POS. Since OR is perpendicular to PQ, therefore we have PoR equal to angle TOS. Now PoR can be written as sum of angles POS and ROS and PoR can be written as angle SOQ minus angle ROS. Taking ROS from the left hand side we have 2 times of angle ROS is equal to angle SOQ minus angle POS which is further equal to angle ROS is equal to half of angle SOQ minus angle POS. Hence we have angle ROS equal to half of angle TOS minus angle POS. So this completes the solution. Hope you enjoyed it. Take care and bye for now.