tan2x=tan
={tan(x+y) + tan(x-y) } / {1-tan(x+y)tan(x-y)}
=1+tan(x+y)/坦悉哗1-tan(x+y)=3
解得让行陆液 tan(x+y)=1/2
tg(2x)= tg(x+y+ x-y)=[tg(x+y)+tg(x-y)]/[1-tg(x+y)*tg(x-y)]= [tg(x+y)+1]/[1-tg(x+y)*1]=3
解塌伍春团耐得橘脊tg(x+y)+1 = 3-3tg(x+y)
tg(x+y)=1/2
tan2x=2tanx/察正昌败扒1-tanx^2
3tan(x-y)=3[tanx-tany/清御1+tanxtany]=3
tan(x-y)=[tanx-tany/1+tanxtany]=1
tan(x+y)=[tanx+tany/1-tanxtany]
所以tan(x+y)=-tan(x-y)=-1
答案是0.5
答案是1/2