A.s=πdctgβθ/[360(1-πθc/360°)] B.s=πdctgβ/[360°(1-πθc/360°)] C.s=πd D.s=πdctgβθ/{360°[1-(πθc/360°)ctgβ]}
A.15.15 B.20.4 C.22.65 D.17.85
A.0.5 B.0.6 C.0.15 D.1.5