【正文】
0s i n)10s i n2 310c o s21(210c o s10s i n10s i n310c o s ??? =????????? 20s i n )1030s i n(410c os10s i n2 )10s i n30c os10c os30(s i n4 ???=4. =??????? 36s i n4 72c os72s i n236s i n2 72c os36c os36s i n2 ??=41 . sin,然后逐次使用倍角公式 ,則原式 =12sin22sin?nnaa. =sin6176。=sin6176。 = 1616c os16 6c os6c os2 96s i n6