连AD利用圆的切割线定理可知AF^2=FD*FC∵D为EF中点∴FD=DE=3/4CEFC=3/4*2CE+CE=5/2CECE=16倍根号3分之2FE=24倍根号3分之2∵AF为切线∴AE^2+AF^2=FE^2AE=8∵AC弧对的∠ADE=∠ABC ∠AED=CEB∴△AED∽△CEBAE/CE=ED/EBEB=16AB=EB+AE=8+16=24
