As shown in the figure, in △ ABC, BD bisects ∠ ABC, and BD ⊥ AC intersects D, de ∥ BC intersects AB at E. AB = 5cm, AC = 2cm, then the perimeter of △ ade=______ cm.

As shown in the figure, in △ ABC, BD bisects ∠ ABC, and BD ⊥ AC intersects D, de ∥ BC intersects AB at E. AB = 5cm, AC = 2cm, then the perimeter of △ ade=______ cm.

∵ DB bisects ∵ ABC, ∵ abd = ∵ CBD; ∵ BD ⊥ AC, i.e. ∵ ADB = ∵ CDB = 90 °, ∵ a = ∵ C, i.e. △ ABC is isosceles triangle; ∵ D is the midpoint of AC, i.e. ad = 12ac = 1cm; ∵ de ∥ BC, ∵ EDB = ∵ CBD; and ∵ abd = ∵ CBD, ∵ EBD = ∵ EDB, i.e. be = de; ? ade perimeter = AD + de + AE = AD + AE + be = AD + AB = 1 + 5 = 6cm