[R] How to plot two different lines with different color with the same "plot" function?

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Hi,R_Help!
I have done something like this:
>x<-seq(412,612,1)
>plot(x,dpois(x,512),col="blue",type="l")
>plot(x,dnorm(x,512,sd=sqrt(512)),col="red",type="l")
And now,I want to plot the two lines in the same picture or with the same "plot" action?
What should I do? 
And any advises? 	

Thank you in advance!
 				

¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¹ãÐÇ
¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡guangxing at ict.ac.cn
¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡2005-11-23