5). lim(cos 解∵lim(cos-)=lim(cos x→0 lim(1-sin*-)2 x→0 而lim(-sin2 x→0 22 lim(cos14 1 2 (5).lim(cos ) . x x→ x 2 2 2 2 2 2 2 1 1 lim(cos ) lim(cos ) 1 lim(1 sin ) x x x x x x x x x → → →  = = − 解 2 2 1 1 lim( sin ) x 2 2 x →  x 而 −  = − 2 1 2 1 lim(cos )x x e x − →   =