Modeling2

import numpy as np
from math import sin
import matplotlib.pyplot as plt

geg = 9.8
m = 1.0
# c = 10.0
c = 0.0
leg = 140.0
t0 = 0
t_max = 100
n = 1000

x0 = 1
y0 = 0


def f(y):
    return y


def g(x, y):
    return - (geg / leg) * sin(x) - c * y / leg * m


dx, dy = np.zeros(n + 2), np.zeros(n + 2)
dx[0], dy[0] = x0, y0
i, t, dt = 1, t0, t_max / n
while t <= t_max:
    x_, y_ = dx[i - 1], dy[i - 1]
    dx[i], dy[i] = x_ + dt * f(y_), y_ + dt * g(x_, y_)
    t, i = t + dt, i + 1
plt.quiver(dx[:-1], dy[:-1], dx[1:] - dx[:-1], dy[1:] - dy[:-1], scale_units='xy',
           angles='xy', scale=1)
plt.grid()
plt.show()