问题
填空题
计算：
|
答案
sin65°+sin15°sin10° sin25°-cos15°cos80°
=sin65°-
(cos25°-cos5° )1 2 sin25°-
(cos95°+cos65° )1 2
=
sin65°+1 2
cos5°1 2
sin25°-1 2
cos95°1 2
=cos25°+cos5° cos65°-cos95°
=2cos15°cos10° 2sin80°sin15°
=cot15°
=tan75°=2+3
故答案为：2+3