g = graphs.RandomGNM(40, 50)  # 15 vertices and 20 edges
show(g)
g.incidence_matrix()

%time n= factorial(10^7)

%time m=n*n

%var x y z
g = golden_ratio; r = 4.77
p = 2 - (cos(x + g*y) + cos(x - g*y) + cos(y + g*z) +
         cos(y - g*z) + cos(z - g*x) + cos(z + g*x))
show(implicit_plot3d(p, (x, -r, r), (y, -r, r), (z, -r, r),
                plot_points=30, color='orange', mesh=1, opacity=.7), spin=1)

plot(sin)

2/3

sphere()

2+3