def get_activating_points(trace, rcon_alpha):
    """
    Returns a list of time instances where the trace is activated by RCon ⍺
    :param trace: One trace (a list of states in time)
    :param rcon_alpha: A proposition indicating the ⍺ of the RCon
    :return: a list of time instances where the trace is activated
    """

    activation_times = []

    if rcon_alpha == "t_start":
        activation_times = [float("-inf")]      # -∞ is used as a special symbol for t_start
    elif rcon_alpha == "t_end":
        activation_times = [float("inf")]       # +∞ is used as a special symbol for t_end
    else:
        activation_times = [i for i in range(len(trace)) if rcon_alpha in trace[i]]

    return activation_times