求满足方程(tanx)^4+(tany)^4+2(cotx)^2(coty)^2=3+sin^2 (x+y)的所有实数对(x,y)

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求满足方程(tanx)^4+(tany)^4+2(cotx)^2(coty)^2=3+sin^2 (x+y)的所有实数对(x,y)

(tanx)^4+(tany)^4>=2(tanx)^2(tany)^2
2(tanx)^2(tany)^2+2/[(tanx)^2(tany)^2]>=4
3+[sin(x+y)]^2