#!/usr/bin/python3
import numpy as np
import math
import matplotlib.pyplot as plt

def f(x):
    return (x*np.cos(x)+x*np.sin(x/2)).item()

a=-5
b=5
N=20

def minbracket(f,a,b,N):
    brackets=[]
    h=(b-a)/N
    for i in range(1,N-1):
        fx=f(a+(i-1)*h)
        fxi=f(a+i*h)
        fy=f(a+(i+1)*h)
        if fxi<fx and fxi<fy:
             brackets.append([a+(i-1)*h,a+(i+1)*h])
    return brackets

print(minbracket(f,-10,10,1000))