问题
解答题
计算：
|
答案
=sin65°+sin15°sin10° sin25°-cos15°cos80°
=cos(10°+15°)+sin15°sin10° sin(15°+10°)-cos15°sin10° cos10°cos15° sin15°cos10°
=
=cos15° sin15°
=cos(45°-30°) sin(45°-30°)
=
×2 2
+3 2
×2 2 1 2
×2 2
-3 2
×2 2 1 2
=2+
+6 2
-6 2
．3