import math


def f(x):
    """
    Compute  x - sin(x) cos(x)  without loss of significance
    """
    if abs(x) < 0.01:
        return 2 * x ** 3 / 3 - 2 * x ** 5 / 15 + 4 * x ** 7 / 315
    return x - math.sin(x) * math.cos(x)