tolong dulu soalnya kurang paham

Luas lingkaran besar

[tex]l1 = \frac{ {144}^{0} }{ {360}^{0} } \times \pi \times {13}^{2} \\ l1 = \frac{2}{5} \times 169\pi \\ l1 = 67.6\pi \: {cm}^{2} [/tex]

Luas lingkaran kecil

[tex]l2 = \frac{ {144}^{0} }{ {360}^{0} } \times \pi \times {12}^{2} \\ l2 = \frac{2}{5} \times 144\pi \\ l2 = 57.6\pi \: {cm}^{2}[/tex]

Luas daerah diraster

[tex] = (67.6\pi - 57.6\pi) \: {cm}^{2} \\ = 10\pi \: {cm}^{2} [/tex]

luas daerah yang diarsir
= luas juring lingkaran besar - luas juring lingkaran kecil.
= 144/360 phi.13^2 - 144/360.phi.12^2
= 144/360.22/7 (13^2 - 12^2)
= 144/360.phi (169 - 144)
= 144/360.phi.25
= 144/72.5.phi
= 2.5.phi
= 10 phi cm^2....(c,)