#====================
# Figure 9.6.R.
# Plot of tangent function.
#====================
th.lo=-4*pi
th.hi=4*pi
theta=th.lo+(th.hi-th.lo)*(0:1000)/1000  # Values of theta ranging
                                         #  from -4*pi to +4*pi.
y=tan(theta)
plot(theta,y,type="p",ylim=c(-2,2),xlab="theta",
  ylab="tangent")