- #1
AGNuke
Gold Member
- 455
- 9
If [tex]\lim_{x \to 0}\frac{e^{nx}+e^{-nx}-2cos\frac{nx}{2} - kx^2}{sinx - tanx}[/tex] exists and finite, then possible values of 'n' and 'k'
By far, I have got one equation relating n and k.
[tex]\frac{5n^2}{4}-k=0[/tex]
I can simply put choices in there and get answer, but it would be better if I can get answer from the question itself.
By removing the indeterminancy in the denominator and expanding the numerator, I got
[tex]\frac{\left [2\left ( \frac{(nx)^2}{2!}+\frac{(nx)^4}{4!}+... \right )-2\left ( -\frac{(nx/2)^2}{2!}+\frac{(nx)^4}{4!}+... \right ) \right ]cosx}{-\left ( \frac{sinx}{x} \right )\left ( \frac{1-cos^2x}{x^2} \right )x^3}[/tex]
I expanded the series till x3 or x4. I just want an equation which can confirm the value of n, which is probably 2 (as I am getting a fancy answer, k = 5 )
Homework Equations
By far, I have got one equation relating n and k.
[tex]\frac{5n^2}{4}-k=0[/tex]
I can simply put choices in there and get answer, but it would be better if I can get answer from the question itself.
The Attempt at a Solution
By removing the indeterminancy in the denominator and expanding the numerator, I got
[tex]\frac{\left [2\left ( \frac{(nx)^2}{2!}+\frac{(nx)^4}{4!}+... \right )-2\left ( -\frac{(nx/2)^2}{2!}+\frac{(nx)^4}{4!}+... \right ) \right ]cosx}{-\left ( \frac{sinx}{x} \right )\left ( \frac{1-cos^2x}{x^2} \right )x^3}[/tex]
I expanded the series till x3 or x4. I just want an equation which can confirm the value of n, which is probably 2 (as I am getting a fancy answer, k = 5 )
Last edited by a moderator: