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from sympy import *
import math
# center of left circle
x1 = Symbol('x1')
y1 = Symbol('y1')
# center of right circle
x2 = Symbol('x2')
y2 = Symbol('y2')
# left tangent points
x3 = Symbol('x3')
y3 = Symbol('y3')
# right tangent points
x4 = Symbol('x4')
y4 = Symbol('y4')

chainlength = 20
leftdegree = 20
rightdegree = 12
leftr = chainlength/2/math.sin(leftdegree*math.pi/180/2)
rightr = chainlength/2/math.sin(rightdegree*math.pi/180/2)
#print(leftr,"\n",rightr)
# tangent line is 10 sets of chain
len34 = 10*chainlength
# (x3-x4)**2+(y3-y4)**2-len34**2 表示 (x3, y3) 與 (x4, y4)距離 len34
# (x1-x3)**2+(y1-y3)**2-(leftr)**2 表示 (x1, y1) 與 (x3, y3) 距離為左圓半徑
# (x2-x4)**2+(y2-y4)**2-(rightr)**2 表示 (x2, y2) 與 (x4, y4) 距離為右圓半徑
# (x1-x4)**2+(y1-y4)**2-len34**2-(leftr)**2 表示左圓心與兩個相切點所圍成直角三角形邊長關係
# (x2-x3)**2+(y2-y3)**2-len34**2-(rightr)**2 表示右圓心與兩個相切點所圍成直角三角形邊長關係

answer = solve([(x3-x4)**2+(y3-y4)**2-len34**2, \
(x1-x3)**2+(y1-y3)**2-(leftr)**2, \
(x2-x4)**2+(y2-y4)**2-(rightr)**2, \
(x1-x4)**2+(y1-y4)**2-len34**2-(leftr)**2, \
(x2-x3)**2+(y2-y3)**2-len34**2-(rightr)**2, y1, x2, y2], \
[x1, y1, x2, y2, x3, y3, x4, y4])

for i in range(len(answer)):
    print(answer[i])


    

    




---------------------------------------------------------------------------
ImportError                               Traceback (most recent call last)
<ipython-input-1-0fe682989e16> in <module>()
----> 1 from sympy import *
      2 import math
      3 # center of left circle
      4 x1 = Symbol('x1')
      5 y1 = Symbol('y1')

ImportError: No module named 'sympy'

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