We have indeterminateness of type
0/0,
i.e. limit for the numerator is
x→0+limsin(5x)=0and limit for the denominator is
x→0+lim(4x2)=0Let's take derivatives of the numerator and denominator until we eliminate indeterninateness.
x→0+lim(4x2sin(5x))=
Let's transform the function under the limit a few
x→0+lim(4x2sin(5x))=
x→0+lim(dxd4x2dxdsin(5x))=
x→0+lim(8x5cos(5x))=
x→0+lim(8x5)=
x→0+lim(8x5)=
∞It can be seen that we have applied Lopital's rule (we have taken derivatives with respect to the numerator and denominator) 1 time(s)