sinθ+cosθ=-√6/3-√3/3（解释一下：负的三分之根号六减去三分之根号3）这个方法有点死,不过懒得动脑筋了,你凑合着用吧~由（sin^2θ+cos^2θ）^2=1^2=1=sin^4θ+cos^4θ+2sin^2θcos^2θ又sin^4θ+cos^4θ=5/9 则2...