>>908
　π/6 < x < π/3
　3/π < 1/x < 6/π
これと
　∫[π/6,π/3] tan(x)dx = [ -log{cos(x)} ](π/6,π/3)
　= log{cos(π/6)/cos(π/3)}
　= log(√3)
　= (1/2)log(3),
から出る。