AD=BD,则∠DAB=∠B.设∠DAB=∠B=X(度),则∠CDA=∠DAB+∠B=2X.又AC=CD,则∠CAD=∠CDA=2X,故∠BAC=3X.又AB=AC,则∠C=∠B=X.∵∠BAC+∠B+∠C=180°.即3X+X+X=180, X=36.∴∠BAC=3X=108°.
