*ABC*is an acute-angled triangle inscribed in a circle and

*P*,

*Q*,

*R*are the midpoints of the minor arcs

*BC*,

*CA*,

*AB*respectively.

Prove that

*AP*is perpendicular to

*QR*.'

I know that the lines from the midpoints to the centre of the circle are perpendicular bisectors of the sides of the triangle

but I'm struggling to know how to use this.