原式=1-sin²36 sin²18
=1 (sin18 sin36)(sin18-sin36)
=1 [sin(27-9) sin(27 9)][sin(27-9)-sin(27 9)]
=1 (sin27cos9-cos27sin9 sin27cos9 cos27sin9)(sin27cos9-cos27sin9-sin27cos9-cos27sin9)
=1-4sin27cos9cos27sin9
=1-(2sin27cos27)(2sin9cos9)
=1-sin18sin54
=1-2sin18cos18cos36/2cos18
=1-sin36cos36/2cos18
=1-sin72/4sin72
=1-1/4
=3/4。
答：--1 2/1 =-1-(- 1/2) -1 /2详情>>
答：详情>>
