Question

How to prove this sum ???

Answer 1

`\text{PROVE:}\ \angle ROS=(1)/(2)(\angle QOS-\angle POS)\\\\\angle QOR=90^o\\\angle QOS=90^o+\angle ROS\\\angle POS=90^o-\angle ROS\\\\\text{substitute}\\\\\angle ROS=(1)/(2)[90^o+\angle ROS-(90^o-\angle ROS)]\\\angle ROS=(1)/(2)(90^o+\angle ROS-90^o+\angle ROS)\\\angle ROS=(1)/(2)(2\angle ROS)\\\angle ROS=\angle ROS`