∵DE⊥AB,DF⊥AC∴∠AED=90°=∠AFD∴∠AED+∠AFD=180°∴点A,E,D,F四点共圆∴∠AFE=∠ADE∵∠B+∠BDE=90°∠BDE+∠ADE=90°∴∠B=∠ADE∴∠AFE=∠B
