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2011-12-18 · 知道合伙人教育行家
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△PQR是圆O的内接【正三角形】,四边形ABCD是圆O的内接【正四边形】,BC平行QR,
∠AOB=90°,∠PQR=60°
做OM平行QR与AQB弧交于M
∠AOM =∠AOB/2 = 90°/2 = 45°
又:∠OQR =∠PQR/2 = 60°/2 = 30°
OM平行QR
∠MOQ = ∠OQR = 30°
∠AOQ = ∠AOM+∠MOQ = 45°+ 30° = 75°
∠AOB=90°,∠PQR=60°
做OM平行QR与AQB弧交于M
∠AOM =∠AOB/2 = 90°/2 = 45°
又:∠OQR =∠PQR/2 = 60°/2 = 30°
OM平行QR
∠MOQ = ∠OQR = 30°
∠AOQ = ∠AOM+∠MOQ = 45°+ 30° = 75°
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