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问题 填空题

小白兔每跳一次为1米，先沿直线跳12次后左拐，再沿直线向前跳5次后左拐，最后沿直线向前跳13次正好回到原来的地方，则小白兔第一次左拐的角度是______度．

答案

由题意得：小白兔第一次跳12米，第二次跳5米，第三次跳13米；

∵

122+52
=13米，

而132=169，刚好符合直角三角形中勾股定理的逆定理，且第一次和第二次跳的距离为直角边．

故小白兔第一次左拐的角度是90°．

阅读理解

On March 31, 2013, the Centre for Health Protection (CHP) of the Department of Health of Hong Kong and the Chinese National Health and Family Planning Commission notified(通知) the World Health Organization of three confirmed human cases of influenza A (H7N9) in Shanghai and Anhui. On April 2, the CHP confirmed four more cases in Jiangsu province.

The first reported death associated(与……有联系) with H7N9 was an 87-year-old man who died on March 4. A second man, Wu Liangliang, aged 27, died on March 10. On April 3, Chinese government reported another death, bringing the number to three. On April 4, the number of reported cases was 14, with 5 deaths. On April 6, 2013, the Chinese Ministry of Health reported 18 positive cases, death toll still at 6. Two days later, positive cases rose to 24 and one death case from Shanghai brought the death toll to 7.

The World Health Organization reiterated(重申) there was still no evidence of human-to-human transmission(传播) of the new strain of H7N9 bird flu.

小题1:The first person died of H7N9 on ______________.

A．March 4

B．March 10

C．March 31

D．April 2小题2:On April 26, the number of reported cases was _________.

A．115

B．118

C．120

D．128
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问答题 简答题

电流互感器运行时造成二次开路的原因有哪些？
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