题解 | 三角形面积

import math

class Point:
    def __init__(self, x, y):
        self.x = x
        self.y = y

class Triangle:
    def __init__(self, a, b, c):
        self.a = a
        self.b = b
        self.c = c

def get_area(T):
    # TODO: 计算三角形T的面积
    #海伦公式
    ab = ((T.a.x-T.b.x)**2+(T.a.y-T.b.y)**2)**0.5
    bc = ((T.b.x-T.c.x)**2+(T.b.y-T.c.y)**2)**0.5
    ca = ((T.c.x-T.a.x)**2+(T.c.y-T.a.y)**2)**0.5
    lv = (ab+bc+ca)/2
    s = (lv*(lv-ab)*(lv-bc)*(lv-ca))**0.5
    return s
    #pass














































































































































































































































































































































def main():
    x, y = map(int, input().split())
    a = Point(x, y)
    
    x, y = map(int, input().split())
    b = Point(x, y)
    
    x, y = map(int, input().split())
    c = Point(x, y)
    
    T = Triangle(a, b, c)
    print("{:.2f}".format(get_area(T)))

if __name__ == "__main__":
    main()