<p>What does Point P and Q are symmetric about line AB mean? Like how is PQ + QR = 4?</p>
<p>The distance between p and q is equally divided by the border of the rectangle, in other words the distance from p to line AB is the same as the distance from q to AB. Same with q and r with CD .</p>
<p>PQ + QR would be 8. BC is already 4, and reflected across lines AB and CD would not change BC's length. p to AB + R to CD = 4, since it's just BC reflected over AB and CD in segments.</p>
<p>So PQ + QR = 4 + 4 = 8</p>