∠A的度数是 80°
∠LBC+LCB=180-BLC=50°
∠ABL=∠LBC
∠ACL=∠LCB
∠ABC+∠ACB=∠ABL+∠LBC+∠ACL+∠LCB=100°
所以∠BAC=180-∠ABC-∠ACB=80°