from sympy import init_printing,plot,limit,oo
init_printing(pretty_print=True)
%matplotlib inline
from sympy.abc import a,n
from sympy import tan,pi
expr = n / (4*tan(pi/n))
expr
plot(expr, (n,0,1000))
<sympy.plotting.plot.Plot at 0x7f6b2ed4cc10>
limit(expr, n, oo)
expr = n*tan(pi/n)
limit(expr, n, oo)
plot(expr, pi, (n,0,5), ylim=(3,5))
<sympy.plotting.plot.Plot at 0x7f6b2dfb1d90>
expr