长宁区2017历史相同。
如图:连接a' b？打造BF⊥A`E DG⊥AC
∵A`E⊥AC ∴ ∠AED=45
D是AB的中点
∴DG = ge = BC/2 = 3 AE = a ` e = ag+ge = 4+3 = 7
a ` f = a ` e-BC = 1 FB = EC = 1
A`B= √2
∵A`E⊥AC ∴ ∠AED=45
D是AB的中点
∴DG = ge = BC/2 = 3 AE = a ` e = ag+ge = 4+3 = 7
a ` f = a ` e-BC = 1 FB = EC = 1
A`B= √2