It displays how derivative values propagate according to the chain rule in en:automatic differentiation for the function

${\displaystyle f(x_{1},x_{2})=x_{1}x_{2}+\sin(x_{1})}$

${\displaystyle {\bar {f}}=1}$

${\displaystyle f(x_{1},x_{2})}$

${\displaystyle \partial f/\partial x_{1}=x_{2}+\cos(x_{1})}$

${\displaystyle x_{1}}$

${\displaystyle \partial f/\partial x_{2}=x_{1}}$

${\displaystyle x_{2}}$