- #1
matematikuvol
- 192
- 0
Homework Statement
[tex]\frac{d^{2n}}{dx^{2n}}\cos x[/tex]
[tex]n \in N[/tex]
Homework Equations
[tex]\cos x=\sum^{\infty}_{k=0}(-1)^k\frac{x^{2k}}{(2k)!}[/tex]
The Attempt at a Solution
[tex]\frac{d^{2n}}{dx^{2n}}x^{2n}=(2n)![/tex]
But k is different that [tex]n[/tex]. I don't have a clue how to solve that.