1).cosx≠0. x≠kπ+π/2.k∈Z. ∴f(x)的定义域为{x│x≠kπ+π/2.k∈Z}. 2)α是第四象限的角,切tanα=-4/3. sinα=-4/5, cosα=3/5. sin2α=2sinαcosα=-24/25. cos2α=2cos^2-1=-7/25. √2sin(2x-π/4）=√2(sin2...