Perhatikan gambar berikut!

`Bangun datar

α = 72°

r = 14 cm

Luas juring

» α/360° × Luas lingkaran

» 72°/360° × π × r × r

» 1/5 × 22/7 × 14 × 14

» 1/5 × 22 × 2 × 14

» 1/5 × 616

» 616/5

» 123,2 cm² (A)

L.j = a/360° × (π × r × r)

L.j = 72°/360° × (22/7 × 14 × 14)

L.j = (72/360)° × (22(14/7) × 14)

L.j = (72/360)° × (22(2) × 14)

L.j = (72/360)° × (44 × 14)

L.j = 72/360 × 616

L.j = 123,2 (Opsi (A))