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从O点引射线OA,OB,OC.已知∠AOB=90°,又∠AOB与∠BOC的平分线所成的角 ∠EOF=60°,则∠BOC的度数是
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A.30° B.45° C.15° D.20°
计算:
(7)22.54+(-4.4)+(-12.54)+4.4;