Question

选择：在梯形ABCD中,AD‖BC,AB=DC=BC,E是AB、DC延长线的交点,若∠E=40°,则∠ACD= °

Answer 1

选B 75°

梯形ABCD为等腰梯形（AB=CD)

∠B=∠D=(180°-40°)/2=70°

∠EBC=70°

因为 BA=BC

所以 ∠BAC=∠BCA

2∠BAC=∠BAC+∠BCA=∠EBC=70°

∠BAC=35°

∠ACD=180°-∠CAD-∠D=180°-(∠A-∠BAC)-∠D=180°-(70°-35°)-70°=75°