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问题 填空题
若△ABC的周长等于20，面积是10
3
，A=60°，则a=______．
答案

∵A=60°，

∴S△ABC=

1
2
bcsinA=10
3
，即
3
4
bc=10
3

解之得bc=40

由余弦定理a2=b2+c2-2bccosA，得

a2=（b+c）2-3bc=（b+c）2-120

∵△ABC的周长a+b+c=20

∴b+c=20-a，得a2=（20-a）2-120，解之得a=7

故答案为：7

单项选择题

NAC’s (Network Access Control)role is to restrict network access to only compliant endpoints and (1) users. However, NAC is not a complete LAN (2) solution; additional proactive and (3) security measures must be implemented. Nevis is the first and only comprehensive LAN security solution that combines deep security processing of every packet at 100Gbps, ensuring a high level of security plus application availability and performance. Nevis integrates NAC as the first line of LAN security (4) In addition to NAC, enterprises need to implement role--based network access control as well as critical proactive security measures-real-time, multilevel (5) inspection and microsecond threat containment.

(2)

A．crisis

B．security

C．favorable

D．excellent
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填空题

常温下挥发油多为（）色或（）色的（），具有较强的（）气味。
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