1· 若sinθ+cosθ=1／2,求tanθ+1／tanθ的值.

1.(sinθ)*2+(cosθ)*2=1
=(sinθ+cosθ)*2-2sinθ.cosθ,
sinθ.cosθ=-3/8
tanθ+1／tanθ
=sinθ/cosθ+cosθ/sinθ
=1/sinθ.cosθ=-8/3
2.题中等式可化为sinθ/|sinθ|+|cosθ|/cosθ=0
sinθ在（0,π）大于零,（π,2π）小于零
cosθ在（0,π/2）和（3π/2,2π)大于零,（π/2,3π/2)小于零
因此θ在（π/2,π）和（3π/2,2π)满足等式