Hoplite - History of the word

[Paralus]

It is a mistake to take "wedge" too literally in ancient writers accounts, for whilst it can be a literally true description of, say, a cavalry formation such as Alexander's, it is also used to describe pretty much any formation deeper than it is long.....

I'd agree with the caveat that I do think that Alexander did form a wegde of sorts - in the more literal sense - at Gaugamela. The cavalry being the apex and the hypaspists one side down to the brigade of Koinos. The right wing was already laid back by the Persian assault and so, one would think, any assualt by the companion cavalry and a line refused to the left would resemble something triangular. The effect was rather frightening if we believe Arrian:

[...] but when the Macedonian cavalry, commanded by Alexander himself, pressed on vigorously, thrusting themselves against the Persians and striking their faces with their spears, and when the Macedonian phalanx in dense array and bristling with long pikes had also made an attack upon them, all things together appeared full of terror to Darius...

This would be his "wedge" driving into and through the Persian array.