Choosen As Best Answer

r = 1 => π
r = 3 => 3π
r = 5 => 5π
r = 7 => 7π
...
d = 2π
an = a1 + (n-1)×d
= π + (n-1)×2π
= 2nπ - π

π/分鐘 => 60π/小時

Sn = (π + 2nπ - π) × n ÷ 2 ≧ 60π (總和要比要求的多)
n^2 ≧ 60

n = 8 => 1(順), 3, 5(順), 7, 9(順), 11, 13(順), 15(逆)

110會考戰士🏆

謝謝

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