[Rd] can't plot a line

[Spencer Graves]

Consider the following: 

      plot(0, 0, xlim=c(-10, 10), ylim=c(-50, 50))
      lines(c(0,0), (2*c(-pi, pi))^2)

      I see no line in this plot. 

R version 2.4.1 (2006-12-18)
i386-pc-mingw32

locale:
LC_COLLATE=English_United States.1252;LC_CTYPE=English_United 
States.1252;LC_MONETARY=English_United 
States.1252;LC_NUMERIC=C;LC_TIME=English_United States.1252

attached base packages:
[1] "stats"     "graphics"  "grDevices" "utils"     "datasets"  "methods" 
[7] "base"    

      My work around is the following: 

      pi2.2 <- (2*pi)^2
      lines(c(0, 0), c(-pi2.2, pi2.2))

      Why won't "lines(c(0,0), (2*c(-pi, pi))^2)" work for me? 
      Thanks,
      Spencer Graves