Solving Limit of (1-cos(2x^2)) / (1-cos(3x^2)): Is There Another Way?

  • Thread starter Thread starter kira137
  • Start date Start date
  • Tags Tags
    Limit
kira137
Messages
16
Reaction score
0

Homework Statement


Find

limit ...(1-cos(2x^2)) / (1-cos(3x^2))
x->0

2. The attempt at a solution
since the above gave me 0/0, I used l'Hopital method..
then i got

(4x)sin(2x^2) / (6x)(sin3x^2)
which gives me 0/0 again..

so I kept on using l'Hopital.. but it seemed on going forever

is there other way to solve this..?
thank you in advance
 
Physics news on Phys.org
kira137 said:

Homework Statement


Find

limit ...(1-cos(2x^2)) / (1-cos(3x^2))
x->0

2. The attempt at a solution
since the above gave me 0/0, I used l'Hopital method..
then i got

(4x)sin(2x^2) / (6x)(sin3x^2)
which gives me 0/0 again..

so I kept on using l'Hopital..

Don't keep using LH rule. Remember you know (at least you should know):

\lim_{x\rightarrow 0}\frac {\sin x} x = 1

See if you can figure out how to use that next.
 
Using LH twice doesn't give 0/0.
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
Back
Top