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