A circle has points P, Q, R on a circle in such a way that angle PQR is 60 deg and angle QRP is 80 deg. Calculate the angle subtended by an arc QR at the centre.
Calculate the length (in cm) of the chord of the circle which is at the distance of the 12 cm from the centre and at the radius of the circle is 13 cm.
The length of a mirror arc is 2/9 of the circumference of the circle. Write the measure of the angle (in degrees) subtended by the arc at the centre of the circle.