1）tan(x-y)=(tanx-tany)/(1+tanxtany)=2tany/(1+3tan^2y)=2/(1/tany+3tany)≤2/2√(1/tany*3tany)=1/√3=√3/3=tanπ/6x-y的最大值为：π/62)（x^2/y^2）+(y^2/x^2)=（x/y+y/x)^2-23[（x^2/y^2）+(y^2/x^2)]-8[(x/y...