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问题 填空题

已知扇形的半径为3cm，圆心角为120°，则此扇形的弧长是______cm．

答案

∵L=

nπr
180
，扇形的半径为3cm，圆心角为120°，

∴扇形的弧长L=

3×π×120
180
=2π．

故答案为：2π．

单项选择题

In data communication, data link is those parts of two data terminal equipments that are controlled by a protocol along with the (71) data circuit, which together enable data (72) . So-called protocol means, in short, a set of rules that determines the behavior of functional units in achieving communication.

Data circuit, however, consists of a pair of (73) transmission channels that provides a means of two-way data transmission. Between data switching exchanges, the data circuit may or may not include data circuit-terminating equipment (DCE), depending on the type of (74) used at the data switching exchange. Between a data station and a data switching exchange or data concentrator, the data circuit includes the DCE at the data station end, and may include equipment (75) to a DCE at the data switching exchange or dam concentrator location.

（72）处填（）。

A．transfer

B．transmission

C．passing

D．delivery
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判断题

x^2+x+1在有理数域上是可约的。
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