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

def f(x):
    left_side = 2*np.cos(x + (np.pi/6)) + x**2
    right_side = 4 * x - 3
    return left_side - right_side

def oblicz(a,b):
    x1,x2 = a,b
    x = 0
    epsi = 0.01

    while(fabs(f(x)) > epsi):
        x = (x1 + x2) / 2
        y = f(x)
        y1 = f(x1)
        if y*y1 < 0:
            x2 = x
        elif y*y1 > 0:
            x1 = x
    return x

a,b = -2,7

print(f"Pierwiastek: {round(oblicz(a,b), 4)}")

x = np.linspace(-15, 15, 1000)
y = f(x)

plt.figure(figsize=(10, 6))
plt.plot(x, y, label=r"$f(x) = 2\cos(x + \frac{\pi}{6}) + x^2 - (4x - 3)$", color="blue")
plt.axhline(0, color="black", linestyle="--", linewidth=0.8)  # Add x-axis
plt.axvline(0, color="black", linestyle="--", linewidth=0.8)  # Add y-

plt.axvline(a, color="red", linestyle="-", linewidth=2, label="a = {:.2f}".format(a))
plt.axvline(b, color="green", linestyle="-", linewidth=2, label="b = {:.2f}".format(b))

plt.title("Bisekcja")
plt.xlabel("x")
plt.ylabel("f(x)")
plt.legend()
plt.grid()
plt.show()