∵AB‖CD
∴∠DAB+∠ADC=180 (两直线平行,同旁内角互补)
又AE平分∠DAB,DE平分∠ADC
∴∠DAE=∠DAB/2,∠ADE=∠ADC/2
∴∠DAE+ ∠ADE=∠DAB/2+∠ADC/2=(∠DAB+∠ADC)/2=90
∴∠AED=180-(∠DAE+∠ADE)=180-90=90
∴DE⊥AE
∵AB‖CD
∴∠DAB+∠ADC=180 (两直线平行,同旁内角互补)
又AE平分∠DAB,DE平分∠ADC
∴∠DAE=∠DAB/2,∠ADE=∠ADC/2
∴∠DAE+ ∠ADE=∠DAB/2+∠ADC/2=(∠DAB+∠ADC)/2=90
∴∠AED=180-(∠DAE+∠ADE)=180-90=90
∴DE⊥AE