问题
填空题
用反证法证明命题：“三角形的内角中至少有一个不大于60°”时，给出了如下四种反设：
（1）假设三内角都不大于60°；
（2）假设三内角都大于60°；
（3）假设三内角至多有一个大于60°；
（4）假设三内角至多有两个大于60°。
则反设正确的序号是（ ）。
答案
（2）
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用反证法证明命题：“三角形的内角中至少有一个不大于60°”时，给出了如下四种反设：
（1）假设三内角都不大于60°；
（2）假设三内角都大于60°；
（3）假设三内角至多有一个大于60°；
（4）假设三内角至多有两个大于60°。
则反设正确的序号是（ ）。
（2）
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| What do the people usually do on weekends? Some people like to 1 at home, but others like to go out for a walk, play football or do some other exercise. Mr Smith 2 hard in a factory during (在期间) the 3 . On the weekends, he usually 4 the same thing. On Saturday he washes his car and on 5 he goes with his family to a village (村庄) by car. His uncle and aunt 6 a farm there. It isn't a big one, but there is always 7 to do on the farm. The children help with the animals and give them some 8 . Mr and Mrs Smith help them do the farm work in the field. At the end of the day, they are all 9 and Mr Smith's aunt 10 them a big meal. | |||
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