inverse linear interpolation method for continuous functions

from math import cos


def tested_function(x):
    return cos(x) - x


def main():
    print('[x0, x1]')
    x0 = float(input('x0 = '))
    x1 = float(input('x1 = '))
    pivot = 0
    iteration = int(input('Number of iteration ?'))
    for i in range(iteration):
        x2 = x1 - tested_function(x1) *\
                (x1 - x0) / (tested_function(x1) - tested_function(x0))
        r = tested_function(x2)
        print('{}'.format(r))
        if r == 0:
            print('done')
            return
        if tested_function(x2) * tested_function(x1) < pivot:
            x0 = x2
        else:
            x1 = x2
        print('[{}, {}]'.format(x0, x1))
        print(x1)


main()