JAMB 2004 · UME · Q29

Determine the locus of a point inside a square $PQRS$ which is equidistant from $PQ$ and $QR$ .

Worked solution (try it first)

$PQ$ and $QR$ meet at the corner $Q$ .
Points equidistant from two lines that meet lie on the bisector of the angle between them, here $\angle PQR$ .
In a square, the diagonal from $Q$ bisects the right angle at $Q$ .
That diagonal is $QS$ , option B.