Răspuns:
Aria sector de cerc = pi • r^2 • u°/360°
a) 3 • pi = pi • 36 • u°/360°
u° = 360° • 3/36
u° = 30
b) 12 • pi = pi • 36 • u°/360°
u° = 360° • 12/36
u° = 120
c) 72 • pi/5 = pi • 36 • u°/360° | • 5
72 • pi = pi • 36 • u°/72°
u° = 72° • 72/36
u° = 144