\begin{Schunk}
\begin{Sinput}
 criticalValue <- mu +1.96 * sigma
 criticalValue <- round(criticalValue, 2)
 ### Then grab all myx values that are "to the left" of that critical value.
 specialX <-  myx[myx >= criticalValue]
 ### mark the critical value in the graph
 text ( criticalValue, 0 , label= paste(criticalValue), pos=1)
 ### Take sequence parallel to values of myx inside critical region
 specialY <- myDensity[myx > criticalValue]
 #  Polygon makes a nice shaded illustration
 polygon(c(specialX[1], specialX, specialX[length(specialX )]), c(0, specialY, 0), density=c(-110), col = "lightgray" )
\end{Sinput}
\end{Schunk}
