f(x)=tanx-cotx =sinx/cosx - cosx/sinx =(sin^2 x -cos^2 x)/sinxcosx =-2(cos2x)/sin2x =-2cot(2x)（1）∵f(-x)==-2cot(-2x)=2cot(2x)=- f(x)∴f(x)是奇函数（2）最小正周期T=π/2
