已知tan2α=1/3二倍角公式：tan2α=2tanα/[1-(tanα)^2]即：2tanα/[1-(tanα)^2]=1/36tanα=1-(tanα)^2(tanα)^2+6tanα-1=0tanα=[-6±√(6^2+4)]/2tanα=-3±√10(tanα)1=-3-√10(tanα)2=(√10)-3...