如图,已知AB//CD,∠B=120°,∠E=80°,求∠C的度数.

网友回答

过E点向左做一条AB的平行线EF
则∠B+∠BEF = 180°
则∠BEF = 180°- ∠B = 60°
∠CEF = ∠E - ∠BEF = 80°- 60° = 20°
因为AB//CD AB//EF
则CD//EF
则∠C = ∠CEF = 20°
======以下答案可供参考======
供参考答案1:
20度!供参考答案2:
过点E做FE//AB
所以∠FBE=180-120=60
所以∠FEC=∠BEC-∠FBE=80-60=20
又AB//CD，所以FE//CD
所以∠C=∠FEC=20°
供参考答案3:
过E点向左做一条AB的平行线EF
则∠B+∠BEF = 180°
则∠BEF = 180°- ∠B = 60°
∠CEF = ∠E - ∠BEF = 80°- 60° = 20°
因为AB//CD AB//EF
则CD//EF
则∠C = ∠CEF = 20°