Draw a diagonal arrow across an expression in a formula to show that it vanishes

Question

I would like to find a way to cross out a term in a mathematical expression with a diagonal arrow pointing from lower left to upper right and with a little "zero" next to the pointy end of the arrow.

Answer 1

You can use the cancel package (adding \usepackage{cancel} in the preamble of the document) that introduces the commands:

• \cancel: draws a diagonal line (slash) through its argument.

• \bcancel: uses the negative slope (a backslash).

• \xcancel: draws an X (actually \cancel plus \bcancel).

• \cancelto{〈value〉}{〈expression〉}: draws a diagonal arrow through the 〈expression〉, pointing to the 〈value〉.

For example, to get an arrow ending in a zero over parameter $\phi$, you would use $\cancelto{0}{\phi}$.