Given \(f\left( z \right) = \frac{{{z^2}}}{{{z^2} \;+ \;{a^2}}}\). Then
1
z = ia is a simple pole and \(\frac{ia}{2}\) is a residue at z = ia of f(z)
2
z = ia is a simple pole ia is a residue at z = ia of f(z)
3
z = ia is a simple pole and \(-\frac{ia}{2}\) is a residue at z = ia of f(z)
4
none of the above