Let $X$ be an algebraic surface, $E$ be a rank $r$ vector bundle over $X$, then the Riemann-Roch formula $$\chi(E)=r\chi(\mathscr O_X)+\frac12\left(c^2_1(E)-c_1(E)c_1(K_X)\right)-c_2(E),$$ holds.
Q: I know how to show it using index theory.
But I do not know how to show it in sheaf language, i.e. by inductive method, construct a sheaf for rank two case.
Could any one help me ?