Question

如图,AB=AC,OB=OC,AD切圆o于D.求证：AC与圆o相切

Answer 1

连接OD,过C作OE⊥AC于E,

∵AB是切线,∴OD⊥AB,

∵AB=AC,∴∠B=∠C,

∵OB=OC,∠BDO=∠CEO=90°,

∴ΔOBD≌ΔOCE,

∴OE=OD,

∴AC是圆O的切线.