Hello,

(this sign < means angle)

the triangle PQS is an isoscele triangle (both legs are radii of the circle).

Therefore <SPQ = <SQP.

Using the theorem of the sum of angles in a triangle you get:

<QSR = 2 * 24° = 48°

Therefore the arc is:

arc(QR) = 48° * (2pi)/360° * (1/2)PR = (4/15)pi * (1/2)PR ≈ 0.8377... * PR