- #1
hoch449
- 13
- 0
Homework Statement
a) Show that the functions [tex]f=sin(ax)[/tex] and [tex]g=cos(ax)[/tex] are eigenfunctions of the operator [tex]\hat{A}=\frac{d^2}{dx^2}[/tex].
b) What are their corresponding eigenvalues?
c)For what values of [tex]a[/tex] are these two eigenfunctions orthogonal?
d) For [tex]a=\frac{1}{3}[/tex] construct a linear operator of [tex]f[/tex] and [tex]g[/tex] which is orthogonal to [tex]f[/tex]
The Attempt at a Solution
a) [tex]\hat{A}f=\frac{d^2}{dx^2}sin(ax)=-a^2sin(ax)[/tex]
[tex]\hat{A}g=\frac{d^2}{dx^2}cos(ax)=-a^2cos(ax)[/tex]
b) the eigenvalues are [tex]-a^2[/tex]
c)orthogonality condition is: [tex]\int f^*gdx=0[/tex]
so to satisfy the above condition [tex]a[/tex] would have to be [tex]\pm\frac{n\pi}{2} \pm\n\pi[/tex] where [tex]n=\pm1,\pm2,\pm3...[/tex]
d) I have no clue how to do this one.. Any help?