# cotangentSheaf(ProjectiveVariety) -- cotangent sheaf of a projective variety

## Description

This function computes the cotangent sheaf of the projective variety X.

As an example we verify Gauss-Bonnet's theorem on a plane quartic curve:

 i1 : X=Proj(QQ[x,y,z]/(x^4+y^4+z^4)) o1 = X o1 : ProjectiveVariety i2 : genus(X) o2 = 3 i3 : omega = cotangentSheaf(X) 1 o3 = OO (1) X o3 : coherent sheaf on X, free i4 : degree omega o4 = 4