Jawabanmu

2014-05-16T20:50:14+07:00
2014-05-16T20:53:42+07:00
GSPL^2 = d^2 - (R-r)^2
12^2 = 13^2 - (R-2)^2
144 = 169 - (R-2)^2
(R-2)^2 = 169 -144
(R-2)^2 =25
R-2 = 5 cm
R = 7 cm