计算lim x的平方减1分之sin(x-1),x区向1

lim(x->1) sin(x-1)/(x^2-1)
=lim(x-1->0) sin(x-1)/(x-1)*1/(x+1)
=lim(x-1->0) sin(x-1)/(x-1)*lim(x->1) 1/(x+1)
=1*1/2
=1/2