A half wavelength dipole is kept in the x-y plane and oriented along 45^{o} from the x-axis. Determine the direction of null in the radiation pattern for $0\leq \phi \leq \pi$. Here the angle $\theta (0\leq \theta \leq \pi )$ is measured from the $z$-axis and the angle$\phi (0\leq \theta \leq 2\pi )$ is measured from the $x$-axis in the $x$-$y$ plane.
1. $\theta =90^{o},\phi =45^{o}$
2. $\theta =45^{o},\phi =90^{o}$
3. $\theta =90^{o},\phi =135^{o}$
4. $\theta =45^{o},\phi =135^{o}$