Jawabanmu

2014-02-16T21:01:02+07:00
R1=2
r2=5
phi ((r2.x)²-(r1.x)²)=63
x²(r2²-r1²)=63/3,14
x²= 63/ (3.14. (r2²-r1²)
x²= 63/ (3.14 (5²-2²)
x²= 63/ (3.14 . 21)
x²= 9.42
x=√9.42

L2= phi. r2²x²
   =(3.14) . ( 25. 9.42)
   = 739,47
2014-02-16T21:45:44+07:00
5:3 x 63
5 x 21
= 105
jawabannya adalah 105