 Differential of the projective quotient map

In the chart $x_j=X_j/X_0$ of Complex projective space, differentiate the quotient coordinates to obtain this formula for $\pi :{\mathbb{C}}^{n+1}\setminus \{0\}\to {\mathbf{P}}^n$. The kernel is the radial line $\mathbb{C}X$. A degree-one homogeneous vector field on the punctured cone descends to a holomorphic vector field, since its scaling cancels the inverse scaling of $d\pi$. This gives the fiberwise construction of the Euler sequence on complex projective space.