limn^2sin^2(θ/n) 当n趋近于无穷的极限怎么算出来的

设t=θ/n,n->∞时t->0
limn^2sin^2(θ/n) =limθ^2(sint/t)^2=θ²lim(sint/t)^2=θ²

limn^2sin^2(θ/n) ,=limθ^2sin^2(θ/n)/θ^2/n^2=,=limθ^2