Can you find the axis of symmetry of the graph of y = arctan(x) + arctan(6 - x)

For those intrepid enough to have gotten this far I offer two hints, which I have encoded for the benefit of those who wish to tackle this problem without them. You can decode the hints at this site You can of course cheat by using a graphing calculator. That still leaves the question of explaining why it works, which requires only a fairly short explanation and does not require any advanced math.

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