# %matplotlib inline
# 建議在jupyterlab中運行
 
import math
import numpy as np
import matplotlib.pyplot as plt
 
def judge(lines):
 """判斷是否能組成三角形"""
 flag = 0
 for i in range(3):
  l1 = lines.copy() # 要copy，不然會對源進行修改
  r = l1.pop(i) # r被取出，l1剩余倆
  if (r>=sum(l1)):
   print("輸入的邊長無法構(gòu)成三角形")
   break
  else:
   flag += 1
   continue
 if flag==3:
  return True
 else:
  return False
 
def plot_triangle():
 lines = input("輸入三條邊長并用空格隔開:")
 params = lines.split(" ")
 lines = list(map(lambda x:float(x),params))
 if judge(lines):
  p = sum(lines)/2
  a,b,c = lines
  area = math.sqrt(p*(p-a)*(p-b)*(p-c))
  width = max(lines)
  height = area/width*2
  # 計算角度
  lines = [a,b,c]
  idx_A = np.argmax(lines)
  A = lines.pop(idx_A)
  # 最長邊作為底部邊長，最左側(cè)與坐標(biāo)軸原點對齊
  B,C = lines
  # 根據(jù)三邊長求兩個水平夾角角度
  cos_C = (A**2+B**2-C**2)/(2*A*B)
  cos_B = (A**2+C**2-B**2)/(2*A*C)
  # 根據(jù)余弦值求得正切值
  k_C = math.tan(math.acos(cos_C))
  k_B = math.tan(math.acos(cos_B))
  # 根據(jù)正切值和高，獲得邊長
  w_C = height/k_C
  w_B = height/k_B
  # 確定三個頂點的坐標(biāo)
  loc_A = (0,height)
  loc_B = (-w_B,0)
  loc_C = (w_C,0)
  plt.figure(figsize=(4,3))
  plt.plot([0,-w_B,w_C,0],[height,0,0,height],"gray")
  plt.plot([0,0],[0,height],"r--")
  plt.text(1,height/2,"h=%.1f"%(height),color="blue",fontsize=12)
  ax = plt.gca()
  ax.set_aspect(1) # 保證兩條坐標(biāo)軸scale一致
  plt.axis('off') # 關(guān)閉顯示直角坐標(biāo)系
  plt.savefig("./trianle.png",dpi=300)
  print("三角形面積為:%.4f"%(area))
 
if __name__=="__main__":
 plot_triangle()

import math
class Triangle:
  def __init__(self):
    a=0
    b=0
    c=0
  def add(self):
      self.a=int(input("輸入第1條邊的長度："))
      self.b=int(input("輸入第2條邊的長度："))
      self.c=int(input("輸入第3條邊的長度："))
      while (self.a+self.b<=self.c):
        print("不符合三角邊的規(guī)定，重新輸入！")
        self.a=int(input("輸入第1條邊的長度："))
        self.b=int(input("輸入第2條邊的長度："))
        self.c=int(input("輸入第3條邊的長度："))
  def out(self):
    print (self.a,self.b,self.c)
  def length(self):
    print (self.a+self.b+self.c)
  def area(self):
    print ((((a+b+c)/2)-a)*(((a+b+c)/2)-b)*(((a+b+c)/2)-c)*((a+b+c)/2))
 
 
t=Triangle()
t.add()
t.out()
t.length()
t.area()