If ABC is an arc of a circle and ∠ABC=135°, then the ratio of arc to the circumference is

If AB is a chord of a circle, P and Q are the two points on the circle different from A and B, then

If two diameters of a circle intersect each other at right angles, then quadrilateral formed by joining their end points is a

The chord of a circle is equal to its radius. The angle substended by this chord at the minor arc of the circle is

PQRS is a cyclic quadrilateral such that PR is a diameter of the circle. If ∠QPR=67° and ∠SPR=72°, then ∠QRS=