3tanx=2tan(2x+y)两边同乘以cosx cos(2x+y)：3sinx cos(2x+y) = 2sin(2x+y) cosx6sinx cos(2x+y) = 4sin(2x+y) cosx6sinx cos(2x+y) + sinx cos(2x+y) = 4sin(2x+y) cosx - sin(2x+y) cosxsinx cos(2x+y) + sin(2x+y...但是题目的确是这样的呢但是还是谢谢了推算步骤如上。第一种条件【3tanx=2tan(2x+y)】下，结果是【sin[2(x+y)] = 5 sin(x+y)】第二种条件【3tanx=2tan(x+y) 】下，结果是【sin(x+y) = 5 siny 】