(x→0) lim (sinx+cosx-1)/(sin3x-x^2)
= (x→0) lim [sinx - 2 sin^2(x/2)] / (sin3x-x^2)
= (x→0) lim [(sinx)/x- sin^2(0.5x)/(0.5x)] / [3(sin3x)/3x - x] 上下同除以 x,利用重要极限(sinx)/x
= (x→0) lim [1-sin(0.5x)] / (3*1-x)
=1/3