y=(sin²x+cos²x)/cos²x+2tanx+1 =tan²x+2tanx+2 =(tanx+1)²+1因为x∈［-π/3,π/4],所以tanx∈[-√3,1]tanx=-1即x=-π/4时y取得最小值1,tanx=1即x=π/4时,y取得最大值5...