Scientists fear rising energy bills may lead to an increase in obesity （肥胖） after discovering a link between poorly-heated homes and higher body -fat． Researchers from the University of St
They wear the latest fashions with the most up-to-date accessories(配饰)．Yet these are not girls in their teens or twenties but women in their sixties and seventies．A generation which w
，tan β=
，那么tan
的值为 .
【解析】tan α=tan(α+β-β)=
=
，所以tan
=
=