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"Starting from rest, a disk rotates about its central axis with constant angular acceleration. In 5.0 s, it rotates 25 rad. During that time, what are the magnitudes of (a) the angular acceleration and (b) the average angular velocity? (c) Wha is the instantaneous angular velocity of the disk at the end of the 5.0 s? (d) With the angular acceleration unchanged, through what additional angle will the disk turn during the next 5.0s?"

I have a problem calculating the value for (a). I have the answer but I am not sure why I am right. Using θ = ω0t+ 1/2αt^2 and solving for a, what is the value to be used for θ? Would it be the given 25 rad. or 25 rad/5 s?