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.
The volume of a right circular cone, whose radius of the base is half of its altitude, and the volume of a hemisphere are equal. The ratio of the radius of the cone to the radius of the hemisphere is
A chord of a circle is equal to its radius. A tangent is drawn to the circle at an extremity of the chord. The angle between the tangent and the chord is