Illustration of the evolution of the three angles before and during the merger. θ_{Lmain, Lorbit}, θ_{Lsat, Lorbit}, and θ_{r, v} are represented by blue, orange, and green lines, respectively. The three gray vertical lines represent the merger time (t_merger) as well as 1 Gyr before (t_merger−1 Gyr) and 1 Gyr after (t_merger+1 Gyr) the merger, consistent with Fig. 1. The gray horizontal line represents 90°. The illustrated merger is the same pair as shown in Figs. 1 and 2.