a) cos(2 arccos(\(\frac{1}{2}\)) - 3 arccos(0) - arccos(-\(\frac{1}{2}\))) = cos(2 * \(\frac{\pi}{3}\) - 3 * \(\frac{\pi}{2}\) - \(\frac{2\pi}{3}\)) = cos(\(\frac{2\pi}{3}\) - \(\frac{3\pi}{2}\) - \(\frac{2\pi}{3}\)) = cos(-\(\frac{3\pi}{2}\)) = cos(\(\frac{\pi}{2}\)) = 0.