Hope you guys can help me out. I have a mathematical expression which I constructed its: $ A_S = \frac{A_{U_{Max}} - A_{U_{Min}}}{U\sqrt{2}} $
Is there a way in which I could mathematically specify along with this equation that if $A_{U_{Max}}=A_{U_{Min}}=$NULL then $A_S = U$? This would then mean that the variable $A_S$ could basically have two values it could either be equal to $U$ on the condition that $A_{U_{Max}}$=NULL and $A_{U_{Min}}$=NULL or it could be something else depending on the values of $A_{U_{Max}}$ and $A_{U_{Min}}$.
Any suggestions would be appreciated.