Jawabanmu

2014-06-09T17:00:28+07:00
Keliling Juring=alpha/360 x K.lingkrn(πD)
12,56=90/360 x 3,14.D
D=12,56/(0,25.3,14)=12,56/ 0.785=16 cm
Jadi r=1/2.D=1/2.16=8 cm
Luas=πr²=3,14.8²=3,14.64= 200.96 cm²