Hello, viet!

Where is your difficulty?

. . . .cosh x -1

lim . ----------- . . . . This goes to 0/0

x→0 . . .x²

Apply L'Hopital:

. . . .sinh x

lim . -------- . . . . This goes to 0/0

x→0 . .2x

Apply L'Hopital again:

. . . .cosh x

lim . -------- . . . . This goes to ½

x→0 . . 2