A wave represented by the equation $y_{1} = a\cos(kx - \omega t)$ is superimposed with another wave to form a stationary wave such that the point $x = 0$ is node. The equation for the other wave is\\
(1) $a\cos(kx - \omega t + \pi)$\\
(2) $a\cos(kx + \omega t + \pi)$\\
(3) $a\cos\left(kx + \omega t + \frac{\pi}{2}\right)$\\
(4) $a\cos\left(kx - \omega t + \frac{\pi}{2}\right)$