问题
解答题
求值：
|
答案
-3 sin220°
+64sin220°1 cos220°
=
+64sin220°(
cos20°-sin20°)(3
cos20°+sin20°)3 sin220°cos220°
=
+64sin220°4(
cos20°-3 2
sin20°)(1 2
cos20°+3 2
sin20°)1 2
sin240°1 4
=
+64sin220°4sin40°sin80°
sin240°1 4
=32cos40°+64•1-cos40° 2
=32