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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def arc_distance(theta_1, phi_1, theta_2, phi_2):
 """ Calculates the pairwise arc distance between all points in vector a and b. """

    temp = np.sin((theta_2-theta_1)/2)**2+np.cos(theta_1)*np.cos(theta_2)*np.sin((phi_2-phi_1)/2)**2
    distance_matrix = 2 * (np.arctan2(np.sqrt(temp),np.sqrt(1-temp)))
    return distance_matrix