已知,如图,BD⊥AM于点D,CE⊥AN于点E,BD、CE交点F,CF=BF,求证:点F在∠A的平分线上.
如图,BE=CF,∠B=∠DEF,∠ACB=∠F,求证:△ABC≌△DFE.
计算: (-2)+—
计算: