Question

一钟表,分针长20cm,50分钟针尖走过的路程是多少?扫过的面积是多少?

Answer 1

L = 2πr*θ/2π = θr =2π*(50/60)*20 = 100π/3 ≈ 104.72 cm

S = π*r^2 * θ/2π = r^2 * θ/2 = 0.5 * 2π*(50/60) * 20^2 = 1047.2 (cm)²