caranya kayk gmna? bantu aku yah kakak kakak semuanya..

Keliling :
[tex] \frac{1}{4} \times \: 2 \times \pi \times r[/tex]
= 1/4 × 2 × 22/7 × 21
= 1/4 × 44 × 3
= 11 × 3
= 33

Luas :
= 1/4 × phi × r^2
= 1/4 × 22/7 × 21 × 21
= 1/4 × 66 × 21
= 1/4 × 1386
= 346,5