Holomorphic differentials on a smooth plane curve (source code)

= Holomorphic differentials on a smooth plane curve

If $f(x,y)=0$ has a smooth projective completion of degree $d$ and $f_y\ne0$, then its holomorphic differentials have basis
$$
x^iy^j\frac{dx}{f_y},
\qquad i,j\geq0,\quad i+j\leq d-3.
$$
The equality $f_xdx+f_ydy=0$ gives the equivalent expressions $-x^iy^jdy/f_x$.