问题 填空题
求值:
sin10°-
3
cos10°
cos40°
=______.
答案

sin10°-
3
cos10°
cos40°
=
2(
1
2
sin10°-
3
2
cos10°)
cos40°

=

2(sin10°cos60°-cos10°sin60°)
cos40°
=
2sin(-50°)
cos40°
=-2

故答案为-2.

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