题目内容：

已知函数f(x)=[1-√2sin(2x-π/4)]/cosx {2}设a是第四象限的角且tana=-4/3,求f(a)的值

优质解答

由tana=-4/3可知:sina=4/5,cosa=-3/5得：sin2a=2sinx*cosx=-24/25cos2a=1-2(sinx)^2=-7/25f(x)=[1-√2sin(2x-π/4)]/cosx =[1-√2(sin2x*cosπ/4-cos2x*sinπ/4)]/cosx=[1-sin2x+cos2x]/cosx=[1+24/25-7/25]/(-3/5)=...