A disk rotates at constant angular acceleration, from angular position θ1 = 10.0 rad to angular position θ2 = 69.0 rad in 6.10 s. Its angular velocity at θ2 is 15.0 rad/s.
a) What was its angular velocity at θ1?
b) What is the angular acceleration?
c) At what angular position was the disk initially at rest?