3.3.L.sagews

from sympy import *
from sympy import N as Num

import matplotlib.pyplot as plt
from numpy import linspace, full_like, array, arange

# pie is better than pi
pie = 2*pi

alpha = var("alpha")

N_rel = S(17)/7*cos(alpha) - S(10)/7

print("\n------ Plot --------------------------")

# array of alphas:
(lim_0, lim_1) = (float(0), float(1.2))
alpha_a = linspace(lim_0, lim_1)

# alphas in degrees:
a_deg_a = alpha_a*360./pie


# N / mg:
N_rel = lambdify(alpha,N_rel,"numpy")
N_rel = array(N_rel(alpha_a))

# alpha, for which N = 0:
a_0 = acos(10./17.)

# Plot:
fig = plt.figure()
tmp = ax1 = fig.add_subplot(111)

# Plot N(alpha):
tmp = ax1.plot(a_deg_a,N_rel, "b-", label="$N / mg$")
# pie = 2 pi
tmp = ax1.plot((a_0*360./pie,),(0.), "o")

# Labels:
tmp = ax1.set_xlabel("$\\varphi / {}^\circ$")
tmp = ax1.legend(loc="best")

# save and show:
plt.savefig('3.3.L_2.svg', transparent=True)
plt.show()