import numpy as np
import matplotlib.pyplot as plt
pi = np.pi


xs = np.linspace(0, 2*pi, 50)
ys = np.sin(xs)
zs = np.cos(xs)

fig, ax = plt.subplots()

ax.plot(xs, ys, label="sin(t)")
ax.plot(xs, zs, label="cos(t)")

ax.set_xlabel("Angle t (radians)", size=12)
ax.set_ylabel("f (t)", size=12)
ax.set_title("The functions sin(t) and cos(t)")
ax.legend()

fig.show()

Alternative use of legend function:ΒΆ

import numpy as np
import matplotlib.pyplot as plt
pi = np.pi


xs = np.linspace(0, 2*pi, 50)
ys = np.sin(xs)
zs = np.cos(xs)

fig, ax = plt.subplots()

ax.plot(xs, ys)
ax.plot(xs, zs)

ax.set_xlabel("Angle t (radians)", size=12)
ax.set_ylabel("f (t)", size=12)
ax.set_title("The functions sin(t) and cos(t)", size=14)

labels=["sin(t)", "cos(t)"]
ax.legend(labels)

fig.show()