- #1
transgalactic
- 1,395
- 0
[tex]
\lim _{x->0} \frac{cos(xe^x)-cos(xe^{-x})}{x^3}\\
[/tex]
[tex]
e^x=1+x+O(x^2)\\
[/tex]
[tex]
e^{-x}=1-x+O(x^2)\\
[/tex]
[tex]
xe^x=x+O(x^2)\\
[/tex]
[tex]
cos(x)=1-\frac{1}{2!}x^2+O(x^3)\\
[/tex]
[tex]
\lim_{x->0} \frac{1-\frac{1}{2!}(x+O(x^2))^2+O(x^3)-1+\frac{1}{2!}(x+O(x^2))^2+O(x^3)}{x^3}
[/tex]
but i don't know how to deal with the remainders
there squaring of them etc..
??
\lim _{x->0} \frac{cos(xe^x)-cos(xe^{-x})}{x^3}\\
[/tex]
[tex]
e^x=1+x+O(x^2)\\
[/tex]
[tex]
e^{-x}=1-x+O(x^2)\\
[/tex]
[tex]
xe^x=x+O(x^2)\\
[/tex]
[tex]
cos(x)=1-\frac{1}{2!}x^2+O(x^3)\\
[/tex]
[tex]
\lim_{x->0} \frac{1-\frac{1}{2!}(x+O(x^2))^2+O(x^3)-1+\frac{1}{2!}(x+O(x^2))^2+O(x^3)}{x^3}
[/tex]
but i don't know how to deal with the remainders
there squaring of them etc..
??