【正文】
xx 這一題目運用了解三角函數(shù)題目時常用的方法“切割化弦” 奎屯王新敞 新疆 (3)???? ???? 2222 ta nta nc o ss in )s in ()s in ( ??? ???? ???????? 2222 t a nt a nc o ss in )s inc o sc o s) ( s ins inc o sc o s( s in ???? ???? ?????? ???? 22222222222222t a nt a nc o ss in s inc o s1t a nt a nc o ss in s inc o sc o ss in ?????? 1ta nta nta nta n1 2222 ???? ???? 2 奎屯王新敞 新疆 (1)?? ???? ?? ta nta n1 ta nta n)c o s ( )s in ( ? ???? (2)tan( α + β ) tan( α - β )( 1- tan2α tan2β )= tan2α - tan2β (3) ????? ?? s ins in)c os (2s in )2s in ( ???? 2 奎屯王新敞 新疆證明: (1)右邊= )c o s ( )s in (s ins inc o sc o s s inc o sc o ss inc o ss inc o ss in1c o ss inc o ss in???????????????????????????? (2)左邊= )t a nt a n1)(t a n ()t a n ( 22 ?????? ??? )t a nt a n1(t a nt a n1 t a nt a nt a nt a n1 t a nt a n 22 ???? ???? ?? ??? ??? ?? )t a nt a n1(t a nt a n1 t a nt a n 222222 ???? ?? ??? ?? 右邊??? ?? 22 ta nta n (3)左邊= )c os (2s in ])s in [ ( ??? ??? ???? ? ????????? s in s in)c o s (2s in)c o s (c o s)s in ( ?????? ? ???? ?????? s in ])s in [ (s in s in)c os (c os)s in ( ??????? 右邊????sinsin 3 奎屯王新敞 新疆(1)已知 sin( α + 45176。= 奎屯王新敞 新疆 5 奎屯王新敞 新疆 )6t a n ()6t a n (3)6t a n ()6t a n ( ???????? ?????? = 奎屯王新敞 新疆 6 奎屯王新敞 新疆在 △ ABC 中 , tanA+ tanB+ tanC = 3 3 , ta