Jawabanmu

2014-02-27T06:59:12+07:00
A. K=phi*D=22/7*42=132. b. panjang busur=45/360*132=1/8*132=132/8 cm. c. L=phi*r^2=22/7*21*21=22*3*21=1386. d.luas juring=1/8*1386=1386/8
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2014-02-27T07:07:13+07:00
A keliling lingkara: 2×π×r = 2×22/7×21=132 cm
b.panjang busur=α/360 derajat × kll lingkaran
                       = 45/360×132
                       = 1/8 × 132 =16,5
c.luas juring = α/360 × π.r.r=45/360×22/7.21.21=1/8.1386=173.25 cm²

semoga bermanfaat :D