# What does $c.c.$ mean in this proof?

This is a proof from Wikipedia of Moore-Penrose inverse being the optimal solution of a least squares problem, in which there is a acronym $c.c.$ occurred in some of the equations. Mind if I ask what does that represent?

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Complex Conjugate –  Pragabhava Oct 3 '12 at 6:17

Might be. I don't have a copy at hand, but I prefer $2\Re z$ over $z + \text{c.c.}$. –  martini Oct 3 '12 at 6:24