  Let $G=SL(2;\mathbb{R})$, $P\subset G$ be upper triangular matrices and
$\Gamma\subset G$ be a uniform lattice. A right action of $P$ to
$\Gamma\setminus G$ defines a orbit foliation $\mathcal{F}_P$. We show a
dimensional formula of $H^2(\mathcal{F}_P)$ by using a non-abelian harmonic
analysis on $G$.
