What is the Inclined Mass and Lagrangian for this System?

[getcarter]

Homework Statement

[PLAIN]http://img708.imageshack.us/img708/4375/81747300.jpg
[PLAIN]http://img837.imageshack.us/img837/5850/42434333.jpg
[PLAIN]http://img696.imageshack.us/img696/3518/50793668.jpg

Homework Equations

[PLAIN]http://upload.wikimedia.org/math/1/8/e/18ecb4a5a940ddba19e1c30f8e9ef500.png

The Attempt at a Solution

I couldn't attempt because i am not sure about the constraint equation.

 

[zzzoak]

Due to conservation of impulse in x direction the center of mass of this system
is constant
MX+mx=const.
While m moves right a wedge moves left.

The distance s mass m is moving
s=R$$\phi$$.
Where
$$s=\Delta y / sin \alpha$$.