Question

化简

cos100°

cos5°• 1-sin100°

的结果是 ______．

Answer 1

原式=

cos(90°+10°)

1+cos10° 2 • 1-sin(90°+10°)

=

-sin10°

(1+cos10°)(1-cos10°) 2

=

- 2 sin10°

1-cos210°

=

- 2 sin10°

sin10°

=-

2

．
故答案为：-

2

．