In △ ABC, ab = BC, ∠ a = ∠ C = 45 ° rotate △ ABC clockwise around point B by an angle α (0 ＜ α ＜ 90 °) and △ MBN, BM intersect AC with point E, Mn intersect AC, BC with D and f respectively (1) When α =? EM is the longest; (2) Observe and guess the quantitative relationship between EM and FC in the process of rotation, and explain the reason There should be an answer before 6:30 tomorrow, otherwise it will be invalid

In △ ABC, ab = BC, ∠ a = ∠ C = 45 ° rotate △ ABC clockwise around point B by an angle α (0 ＜ α ＜ 90 °) and △ MBN, BM intersect AC with point E, Mn intersect AC, BC with D and f respectively (1) When α =? EM is the longest; (2) Observe and guess the quantitative relationship between EM and FC in the process of rotation, and explain the reason There should be an answer before 6:30 tomorrow, otherwise it will be invalid

(1) According to the meaning of the title, be + Em = BM = AB, when EM is the longest, be is the shortest, because point E is on AC, be is the shortest when be is vertical to AC, when be is vertical to AC, ∠ Abe = 45 °, that is, α = 45 °
（2）