某实验小组测定中和热做了三次实验,所用NaOH溶液的浓度为0.55mol•L﹣1,盐酸的浓度为0.5mol•L﹣1,每次取NaOH溶液和盐酸溶液各50mL,并记录如表原始数据.
实验序号
起始温度t1/℃
终止温度(t2)/℃
温差(t2﹣t1)/℃
盐酸
NaOH溶液
平均值
1
25.1
24.9
25.0
28.3
3.3
2
28.4
3
28.5
3.4
如图,△AOB中,∠AOB=90°,AO=2,BO=4,△AOB绕顶点O逆时针旋转到△A′OB′处,此时线段A′B′与BO的交点E为BO的中点,则线段B′E的长度为____
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