如图已知△ABC中 ∠A ∠B的平分线交于O 过做OP⊥BC、OR⊥AB、OQ⊥AC,AB=7 BC=8,AC=9 若B
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如图已知△ABC中 ∠A ∠B的平分线交于O 过做OP⊥BC、OR⊥AB、OQ⊥AC,AB=7 BC=8,AC=9 若BO的延长线交AB
于F,角A=60,求证:OE=OF
![](http://img.wesiedu.com/upload/e/78/e78d3a3047ae873813aca5031c5fe071.jpg)
于F,角A=60,求证:OE=OF
![](http://img.wesiedu.com/upload/e/78/e78d3a3047ae873813aca5031c5fe071.jpg)
![如图已知△ABC中 ∠A ∠B的平分线交于O 过做OP⊥BC、OR⊥AB、OQ⊥AC,AB=7 BC=8,AC=9 若B](/uploads/image/z/3029592-48-2.jpg?t=%E5%A6%82%E5%9B%BE%E5%B7%B2%E7%9F%A5%E2%96%B3ABC%E4%B8%AD+%E2%88%A0A+%E2%88%A0B%E7%9A%84%E5%B9%B3%E5%88%86%E7%BA%BF%E4%BA%A4%E4%BA%8EO+%E8%BF%87%E5%81%9AOP%E2%8A%A5BC%E3%80%81OR%E2%8A%A5AB%E3%80%81OQ%E2%8A%A5AC%2CAB%3D7+BC%3D8%2CAC%3D9+%E8%8B%A5B)
∵∠OEQ=∠ABC+∠CBE=∠ACB+1/2∠ABC=∠ACB+1/2(180°-∠A-∠ACB)=60°+1/2∠ACB
∠OFR=∠A+∠ACF=60°+1/2∠ACB
∴∠OEQ=∠OFR
∵OQ=OR,∠OQE=∠ORF=90°
∴△EOQ≌△FOR(AAS)
∴OE=OF
∠OFR=∠A+∠ACF=60°+1/2∠ACB
∴∠OEQ=∠OFR
∵OQ=OR,∠OQE=∠ORF=90°
∴△EOQ≌△FOR(AAS)
∴OE=OF