题目内容
先化简，再求值：(
+1)÷(1-
)•
，其中x=
sin45°•cot60°．
| x |
| x+1 |
| 3x2 |
| 1-x2 |
| 1 |
| x-1 |
| 3 |
(
+1)÷(1-
)•
=
÷
•
=
•
•
=
，
∵x=
sin45°•cot60°=
×
×
=
，
∴原式
=
=
+1．
| x |
| x+1 |
| 3x2 |
| 1-x2 |
| 1 |
| x-1 |
| 2x+1 |
| x+1 |
| 1-4x2 |
| 1-x2 |
| 1 |
| x-1 |
=
| 2x+1 |
| x+1 |
| (1+x)(1-x) |
| (1+2x)(1-2x) |
| 1 |
| x-1 |
| 1 |
| 2x-1 |
∵x=
| 3 |
| 3 |
| ||
| 2 |
| ||
| 3 |
| ||
| 2 |
∴原式
| 1 | ||||
2×
|
| 1 | ||
|
| 2 |
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