Jawabanmu

2014-06-03T19:53:57+07:00
Anggap aja

persekutuan luar = CD
jari 1 = CA
jari 2 = DB
jarak kedua pusat = AB

AB kuadrat = √ CD kuadrat + (r1-r2) kuadrat
= √ 12kuadrat + (7-2) kuadrat
= √ 144 + 25
= √ 169 = 13 cm
2014-06-03T19:55:03+07:00
D2=p2 -( R+r)2
144=? ( 7+2)2
144=?- 81
p2=144-81
p2=63
P=√63