# -*- coding: utf-8 -*-
"""
Created on Thu Oct 19 11:22:10 2017

@author: student
"""

import numpy as np
import matplotlib.pyplot as plt
import scipy.optimize as opt

def f(x):
    #return 2.0*x**2-4.0
    return np.cos(10*x)

#a = input('unesi lijevu granicu: ')

xl = 0
#xl = float(a)
#xl = float(input('unesi lijevu granicu: '))
xd = 0.4
print(f(xl), f(xd))

plt.plot([xl], [f(xl)], 'ob') #zahtjevaju listu brojeva pa su u [], iako je to lista koja
plt.plot([xd], [f(xd)], 'ob') #ima samo jedan clan

it = 0

while it < 30:
    xs = (xl+xd)/2
    plt.plot([xs], [f(xs)], 'or') #or je Red, ob je Blue
    plt.annotate(str(it), xy=[xs, f(xs)]) # str pretvara broj u string
    if abs(f(xs)) < 0.01:
        break
    #plt.annotate(it, xy=[xs, f(xs)]) #annotate pise rijec (1) na poziciji (xy =...)

    if f(xs)*f(xl) < 0:
        xd = xs
    else:
        xl = xs
    xs = (xl+xd)/2
    it += 1

#print('rjesenje: f({})={}'.format(xs, f(xs)) )
print('x: ', xs)
print('f(x): ', f(xs))
print('it : ', it)

x_opt = opt.fsolve(f, 0)
print(x_opt)

x_f = np.linspace(0, 0.4, 401) #0.4 u 30
y_f = f(x_f)

plt.plot(plt.xlim(), [0, 0], color='red')

plt. plot(x_f, y_f)

plt.show()