应该是f(x)=(1-3^x)/(1+3^x),
f(x)=[2-(1+3^x)]/(1+3^x)=2/(1+3^x) -1,是减函数,
又f(x)=(8/5)sinθ在x∈[-2,2]上恒有解,
即sinθ=(5/8)f(x),x∈[-2,2]
所以　(5/8)f(2)≤sinθ≤(5/8)f(-2)
即-1/2≤sinθ≤1/2
2kπ-π/6≤θ≤2kπ+π/6或2kπ+5π/6≤θ≤2kπ+7π/6取值范围不是应该用并集吗，为什么用或啊2kπ-π/6≤θ≤2kπ+π/6或2kπ+5π/6≤θ≤2kπ+7π/6O(∩_∩)O谢谢“或”就是“并”