单项选择题
A.πR2θ/360 B.πR2θ/180 C.πR2θ D.πR2θ/2
A.πR2α/360 B.πR2α/180 C.πR2α D.πR2α/2
A.1°=（π/180）rad B.1°=（π/90）rad C.1°=（π/270）rad D.1°=（π/360）rad
A.T B.G C.M D.k
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