Answer
The interference produces a maximum all along path 1.
Work Step by Step
By symmetry, every point on path 1 is an equal distance from $S_1$ and $S_2$
Therefore, the path length difference is zero for all points on path 1.
Since the sources are exactly in phase, the waves will be in phase at all points on path 1.
Therefore, the interference produces a maximum all along path 1.
