∠DAF=(∠C-∠B)/2 [前提:∠C>∠B]证明:∵∠BAC=180-(∠B+∠C),AE平分∠BAC∴∠CAE=∠BAC/2=90-(∠B+∠C)/2∵AD⊥BC∴∠CAD+∠C=90∴∠CAD=90-∠C∴∠DAF=∠CAE-∠CAD (这一步和[前提:∠C>∠B]相关)=90-(∠B+∠C)/2-90+∠C=(∠C-∠B)/21、∵∠B=36, ∠C=76∴∠DAF=(76-36)/2=20°2、∵∠B=X,∠C=Y∴∠DAF=(Y-X)°/2