# Dimension of Secant variety of an irreducible projective curve not contained in a plane

I'm trying to show that this dimension is three, but I'm stuck. Could anyone give me a hint?

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It's great to know that your curve is not contained in a plane, but where exactly is it? And what does curve mean, by the way? –  Georges Elencwajg Aug 8 '12 at 20:21