是不是这样,
fun＝[2/(a+1) + (a+2)/(a² - 1)] / [a/(a-1)]
＝[2(a-1)/(a²-1) + (a+2)/(a² - 1)] / [a/(a-1)] 分子通分
＝[(2a-2 + a+2) / (a² - 1)] / [a/(a-1)]
＝[3a / (a² - 1)] / [a/(a-1)]
＝3 / (a + 1)
代入已知的其中a = tan60°- 2sin30＝√3 - 2×0.5＝√3 - 1
fun＝3 / (a + 1) ＝3 / (√3 - 1 + 1)＝3 / √3＝√3