(1)∵tan2θ= 2tanθ 1-tan2θ =-2 2 ,∴tanθ=- 2 2 或tanθ= 2 ,∵π<2θ<2π, π 2 <θ<π,∴tanθ=- 2 2 .(2)原式= 1+cosθ-sinθ-1 sinθ+cosθ = 1-tanθ 1+tanθ = 1-(- 2 2 ) 1+(- 2 2 ) =3+2 2 .