[R] How to shadow 'power' area?

[Andrej Kastrin]

Dear all,

Suppose I plot two normal distributions (A and B) side by side and add 
vertical line which hipotheticaly represent alpha value; e.g.:

x <- seq(-3.5,5, length=1000)
y <- dnorm(x)
# Plot distribution A
plot(y~x, type='l',axes=F,xlab="",ylab="",lwd=2)
# Plot distribution B
y2 <- dnorm(x-1.5)
lines(y2~x,lwd=2)
# Plot vertical line for alpha value
abline(h=0)
segments(qnorm(.5)+1.5,0,qnorm(.5)+1.5,dnorm(qnorm(.5)))
text(2,0.2,"Power")

Now I want to shadow area labeled as "Power". Any suggestion how to do 
that using 'polygon' function?

Thanks in advance for any suggestion.

Andrej