During an activity, if the initial angle $(q_i)$ of a segment was $180$ degrees, and the final angle $(q_f)$ was $90$ degrees, which equation would you use to solve for angular displacement? $w_f=$aDt$+w_{i}a=\frac{w_f-w_i}{D}t={}_f-{}_{i}Ds=s_f-s_i$