【正文】
= 1616c os16 6c os6c os2 96s i n6c os2 48c os24c os12c os6s i n6c os2444 ????????????? . = )4t a n(2s i nt a n1 )t a n1(c oss i n2t a n1 s i n2c oss i n2 2 xxx xxxx xxx ??? ??? ? ?. ∵1217?x47?,∴35?4?+x2π .又 cos(4?+x)=53, ∴sin(4?+x)=54,tan(4?+x)=34?. ∴sin2x=sin [ 2(4?+x)2?