As shown in the figure, the side length of equilateral △ ABC is 12, ad is the middle line on BC side, M is the moving point on ad, e is a point on AC side, if AE = 4, the minimum value of EM + cm is______ .

As shown in the figure, the side length of equilateral △ ABC is 12, ad is the middle line on BC side, M is the moving point on ad, e is a point on AC side, if AE = 4, the minimum value of EM + cm is______ .

Take the midpoint F of CE and connect DF. ∵ equilateral △ ABC has the side length of 12, AE = 4, ∵ CE = ac-ae = 12-4 = 8, ∵ CF = EF = AE = 4, ad is the median line on the edge of BC, ∵ DF is the median line of △ BCE, ∵ be = 2DF, be ∥ DF, e is the midpoint of AF,