Question: When I plot the function 2/cos(t) using polar coordinates, strange results come up. Why?

I'd like to plot the graph in polar coordinates of the function r=f(t)=2/cos(t), which should be a vertical line parallel to the y-axis. I've tried it with two different commands, and below you can see the results

plot(2/cos(theta), coords = polar)

plot(2/cos(theta), coords = polar)

What is going on here?

I then tried using polarplot from the plots package.

with(plots):

polarplot(2/cos(t), t = 0 .. 2*Pi)

 

Shouldn't the graph be a vertical line at 2?

Notice that if I plot two similar plots

polarplot([1/cos(t), 2/cos(t)], t = 0 .. 2*Pi)

The same result is obtained

 

What is going on here? 

 

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