求极限: limx→1∫x1tan(t2-1)dt

求极限:
limx→1x1tan(t2-1)dt
【正确答案】:limx→1x1tan(t2-1)dt/(x-1)2 =limx→1tan(x2-1)/2(x-1) =limx→12xsec2(x2-1)/2 =1