(1)
DE⊥BC,△BDE∽△CEF
BE=2x/3
(BC/2)/AB=y/3y=1/3
AB=6,BC=4
BE/OB=2/3,BC/AB=2/3
所以OE//AC,
EF⊥AC
所以EF⊥OE,即EF是圆o切线时
(2)
AB=6,BC=4=BE+EC
2x/3+3y=4
即2x+9y-12=0
(1)
DE⊥BC,△BDE∽△CEF
BE=2x/3
(BC/2)/AB=y/3y=1/3
AB=6,BC=4
BE/OB=2/3,BC/AB=2/3
所以OE//AC,
EF⊥AC
所以EF⊥OE,即EF是圆o切线时
(2)
AB=6,BC=4=BE+EC
2x/3+3y=4
即2x+9y-12=0