To solve this problem we must keep in mind the concepts related to angular kinematic equations. For which the angular velocity is defined as
[tex]\omega_f =\omega_i-\alpha t[/tex]
Where
[tex]\omega_f =[/tex] Final angular velocity
[tex]\omega_i =[/tex] Initial angular velocity
[tex]\alpha =[/tex]Angular acceleration
t= time
In this case we do not have a final angular velocity, then
[tex]\omega_i = \alpha t[/tex]
Re-arrange for [tex]\alpha[/tex]
[tex]\alpha= \frac{\omega_i}{t}[/tex]
[tex]\alpha = \frac{910}{0.167}[/tex]
[tex]\alpha = 5449.1 rad\s^2[/tex]
Therefore the mangitude of the angular aceleration is 5449.1rad/s²