∠DAF+∠ADF+∠F=180°
∠EBC+∠ECB+∠E=180°∠E+∠F=360°-(∠DAF+∠ADF+∠EBC+∠ECB) =360°-1/2(∠BAD+∠ADC+∠BCD+∠ABC) =360°-180°=180°
四边形内角和(∠BAD+∠ADC+∠BCD+∠ABC)为360°
∠DAF+∠ADF+∠F=180°
∠EBC+∠ECB+∠E=180°∠E+∠F=360°-(∠DAF+∠ADF+∠EBC+∠ECB) =360°-1/2(∠BAD+∠ADC+∠BCD+∠ABC) =360°-180°=180°
四边形内角和(∠BAD+∠ADC+∠BCD+∠ABC)为360°