訂正
lim[x→0](sin2x/(x+tan3x))
=lim[x→0]{(sin2x - 0)/(x-0)}/{(x+tan3x - 0)/(x-0)}
=2/4
=1/2

(sin2x - 0)/(x-0)
→2*cos(0)=2
(x+tan3x - 0)/(x-0)
→1 + 3/{cos(0)}^2 = 4