Question

1-cos210°

+

1+cos210°

=______．

Answer 1

原式=

1-cos(180°+30°)

+

1+cos(180°+30°)

=

1+cos30°

+

1-cos30°

=

6

2

+

2

2

=

6 + 2

2

．
故答案为：

6 + 2

2