∵AB//CD,∴∠BAD=∠ADC=80 °,∵DE平分∠ADC∴∠EDC=1/2∠ADC=40 °,∵AB//CD,∴∠ABC=∠BCD=n °,∵BE平分∠ABC∴∠EBC=1/2∠ABC=n/2 °,∵∠EBC+∠BED=∠EDC+∠BCD即n/2 °+∠BED=40 °+n °所以∠BED=40 °+n/...