In the acute angle △ ABC, if ∠ C = 2 ∠ B, the value range of CB is______ ．

According to the sine theorem, csinc = bsinb, i.e. c2sinbcosb = bsinb, it is sorted out that CB = 2cosb. When ∠ C is the largest angle, in ∫ acute triangle ABC, ∠ C ＜ 90 ° and ∫ B ＜ 45 ° and when ∫ A is the largest angle, in ∫ acute triangle ABC, ∠ a ＜ 90 ° and ∫ B ＞ 30 ° and ∫ B ＜ 45 ° and ∫ 2cosb ＜ 2cos30 ° the range of CB is (2, 3) So the answer is: (2, 3)

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