diketahui jari-jari 21 cm dan sudut aob 90 derajat tentukanlah a keliling lingkaran b luas lingkaran C panjang busur AB juring aob
A. K=2πr
K=2×22/7×21
K=2×22×3
K=132 cm
B. L=πr^2
L=22/7×21×21
L=22×3×21
L=1386 cm
C. PB AB=90/360 × 2πr
PB AB=1/4×2×22/7×21
PB AB=1/4×2×22×3
PB AB=33 cm
L juring=90/360×πr^2
L juring=1/4×22/7×21×21
L juring=1/4×22×3×21
L juring=1/4×1386
L juring=346,5 cm
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