# probability or statistics – How to find sum of squares of data from a multivariate (Dirichlet) distribution?

Let $$X = Dirichlet(1,1,1)$$ be a tri-variate random variable with Dirichlet distribution with parameters all equal to 1. I need to find what $$X_1^2+X_2^2+X_3^2$$ will be.

I did `TransformedDistribution(x^2+y^2+z^2, {x,y,z}(Distributed)DirichletDistribution({1,1,1}))`, but it doesn’t seem to do anything. What might be the problem?