def PS2Ymu(Pspeed, Sspeed, rho):
    """ Returns the Young's modulus and Poisson coefficient given the P- and
    S-wave speeds.
    """
    Y = rho * Sspeed**2 * ((3 * Pspeed**2 - 4 * Sspeed**2) / (Pspeed**2 - Sspeed**2))
    nu = (Pspeed**2 - 2 * Sspeed**2) / (2 * (Pspeed**2 - Sspeed**2))
    return Y, nu