Figure shown two coherent sources S1 and S2

Figure shown two coherent sources $S_{1}$ and $S_{2}$ which emit sound of wavelength $\lambda$ in phase. The separation between the sources is $3 \lambda$. A circular wire of large radius is placed in such way that $S_{1}, S_{2}$ is at the centre of the wire. Find the angular positions $\theta$ on the wire for which constructive interference takes place.