How do we truncate a polynomial in Maple, that is, obtain only the terms of degree <= n?

For example, if 

then the truncation [P(x)]4 is

and the truncation [P(x)]₂ is

How do we plot the least integer function [x]?

I am referring to a function with the following graph

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)

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? 

Why is it not as simple as

to obtain a result for the cubic root of -8 that is what one would expect: -2?

Instead we obtain

Why doesn't Maple return -2?

Is it possible to write latex equations in MaplePrimes?

Googling for this and also searching here in MaplePrimes didn't turn up any obvious answers to this question. I am coming from using Math Stack Exchange, and I'd like to ask a question about how to write a particular function in Maple.

$f(x)=\begin{cases} 5, x \neq 0 \\  0, x=0 \end{cases} $