Question

求

cos190°•(-sin210°)

cos350°•(-tan585°)

的值．

Answer 1

cos190°•(-sin210°)

cos350°•(-tan585°)

=

cos(180°+10°)•sin(180°+30°)

cos(360°-10°)•tan(360°+225°)

=

(-cos10°)•(-sin30°)

cos10°•tan225°

=

sin30°

tan(180°+45°)

=

sin30°

tan45°

=

1

2

．