题目内容
求值：①sin870°+cos660°+tan1215°-tan（-300°）+cot（-330°）
②
．
②
| sin(2π-θ)•tan(π+θ)•cot(-θ-π) |
| cos(π-θ)•tan(3π-θ) |
①sin870°+cos660°+tan1215°-tan（-300°）+cot（-330°）
=sin（720°+150°）+cos（720°-60°）+tan（-360°+60°）+cot（-360°+30°）
=sin150°+cos（-60°）+tan60°+cot30°
=sin30°+cos60°+tan60°+cot30°
=
+
+
+
=1+2
②
=
=
=
=
=-1
=sin（720°+150°）+cos（720°-60°）+tan（-360°+60°）+cot（-360°+30°）
=sin150°+cos（-60°）+tan60°+cot30°
=sin30°+cos60°+tan60°+cot30°
=
| 1 |
| 2 |
| 1 |
| 2 |
| 3 |
| 3 |
=1+2
| 3 |
②
| sin(2π-θ)•tan(π+θ)•cot(-θ-π) |
| cos(π-θ)•tan(3π-θ) |
=
| sinθ•tanθ•cot(-θ) |
| -cosθ•tan(-θ) |
=
| -sinθ•tanθ•cotθ |
| cosθ•tanθ |
=
| -sinθ | ||
cosθ•
|
=
| -sinθ |
| sinθ |
=-1
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