
We can rewrite the following as:
\[ \angle ROP = \angle ROQ = 90^\circ \]
Since \( \angle ROP = \angle ROQ \), we can write:
\[ \angle POS + \angle ROS = \angle ROQ \]
Now, substituting for \( \angle ROQ \), we get:
\[ \angle POS + \angle ROS = \angle QOS - \angle ROS \]
Rearranging the terms:
\[ \angle SOR + \angle ROS = \angle QOS - \angle POS \]
Thus, we obtain:
\[ 2 \times \angle ROS = \angle QOS - \angle POS \]
Therefore:
\[ \angle ROS = \frac{1}{2} (\angle QOS - \angle POS) \]


