On MathWorld, at http://mathworld.wolfram.com/Chi-SquaredDistribution.html
you can see 4 graphes.
I have no problem to understand what represent the 2 top graphes.
But I don't understand what represent the 2 bottom graphes. I regret that label of Y axe is, for me, not readable !
What are the functions used to draw these 2 graphes ?