Question

△ABC≌△ADE 且 ∠BAD=100°,∠CAE=40°,求∠BAC

Answer 1

因为△ABC≌△ADE

所以∠BAC＝∠DAE

即∠BAE+∠EAC＝∠DAC+∠CAE

因为∠EAC＝∠CAE

所以∠BAE＝∠DAC

因为∠BAD＝∠BAE+∠CAE+∠DAC

所以100°＝∠BAE+40°+∠DAC

＝2∠BAE+40°

∠BAE＝（100°-40°）/2＝30°

∠BAC＝∠BAE+∠CAE

＝30°+40°＝70°