import numpy as np
#已知平行四邊形三個點，求第四個點
#計算兩點之間的距離
def CalcEuclideanDistance(point1,point2):
    vec1 = np.array(point1)
    vec2 = np.array(point2)
    distance = np.linalg.norm(vec1 - vec2)
    return distance
#計算第四個點
def CalcFourthPoint(point1,point2,point3): #pint3為A點
    D = (point1[0]+point2[0]-point3[0],point1[1]+point2[1]-point3[1])
    return D
#三點構成一個三角形，利用兩點之間的距離，判斷鄰邊AB和AC,利用向量法以及平行四邊形法則，可以求得第四個點D
def JudgeBeveling(point1,point2,point3):
    dist1 = CalcEuclideanDistance(point1,point2)
    dist2 = CalcEuclideanDistance(point1,point3)
    dist3 = CalcEuclideanDistance(point2,point3)
    dist = [dist1, dist2, dist3]
    max_dist = dist.index(max(dist))
    if max_dist == 0:
        D = CalcFourthPoint(point1,point2,point3)
    elif max_dist == 1:
        D = CalcFourthPoint(point1,point3,point2)
    else:
        D = CalcFourthPoint(point2,point3,point1)
    return D

print(JudgeBeveling((0,1),(1,0),(1,1)))
print(JudgeBeveling((5,39),(500,35),(496,17)))