As shown in the figure, in △ ABC, AE is the median line, ad is the angular bisector, AF is high, fill in the blanks: (1) be=______ =12______ (2)∠BAD=______ 12______ (3)∠AFB=______ =90°(4)S△ABC=______ S△ABE.

As shown in the figure, in △ ABC, AE is the median line, ad is the angular bisector, AF is high, fill in the blanks: (1) be=______ =12______ (2)∠BAD=______ 12______ (3)∠AFB=______ =90°(4)S△ABC=______ S△ABE.

(1) ∵ AE is the middle line, ∵ be = CE = 12bc, (2) ∵ ad is the angular bisector, ∵ bad = ∠ CAD = 12 ∠ BAC, (3) ∵ AF is high, ∵ AFB = ∠ AFC = 90 °, (4) s △ ABC = BC · af2, s △ Abe = be · af2, ∵ BC = 2be, ∵ s △ ABC = 2S △ Abe