# Inserting if else in a mathematical expression is it possible

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.

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I meant if Aumax and Aumin do not exist . If they do not exist then they are null – Rajeshwar Apr 17 '12 at 3:55
Yes, it is usually used for continuous Probability ditstribution functions – dashdart Apr 17 '12 at 3:57
What is "do not exist"? Like a) in statistics: that data were not explored/missing data? Or shall "does not exist" mean mathematically b): is infinite/singular? Or, c), since "min"/"max" is involved: the "min"/"max" do not exist as denotable numbers in a set/range, and we have to use "sup"/"inf" instead? – Gottfried Helms Apr 17 '12 at 4:02
Like a) in statistics: that data were not explored/missing data. Here its going to be missing data – Rajeshwar Apr 17 '12 at 4:33

$$A_s = \begin{cases} \ U & \text{if A_{U_{Max}} = A_{U_{Min}} = Null},\\ \ \frac{A_{U_{Max}} - A_{U_{Min}}}{U\sqrt{2}} & \text{otherwise} \end{cases}$$
@PZZ is it also possible to specify with the above expression on the line {if $A_{U_{Max}} = A_{U_{Min}} =$ Null} something like and trigger = true to show that if these values are null then trigger is true otherwise its false ? – Rajeshwar Apr 17 '12 at 4:19