In the equation θ = ωt + (1/2)αt², which relates rotational displacement (θ) to initial angular velocity (ω), time (t), and angular acceleration (α), the sign convention for α depends on the direction of rotation.
If the positive direction of rotation is defined as counterclockwise, then the angular acceleration (α) will have a positive value when it is in the same direction as the counterclockwise rotation. In this case, you should use the positive value of α in the equation.
On the other hand, if the positive direction of rotation is defined as clockwise, then the angular acceleration (α) will have a negative value when it is in the same direction as the clockwise rotation. In this case, you should use the negative value of α in the equation.
It's important to align the signs correctly to ensure consistency in your calculations and to correctly represent the direction of rotation.