請問這兩題怎麼證明？ （微積分?

39
a=lim(x->0)_x^4cos(2/x)
lim(x->0)_x^4>=A>=lim(x->0)_x^4*(-1)
0>=A>=0
A=0
40
A=lim(x->0+)_x^(1/2)[1+Sin^2 (2π/x)]
lim(x->0+)_x^(1/2)[1+1]>=A>= lim(x->0+)_x^(1/2)[1+0]
0>=A>=0
A=0
]