7.2.4.3.py

from sympy import *
import sympy as sp
sp.init_printing(use_latex = "mathjax")
E33, E11, e33, v13, v31, s11, s33 = symbols("E_{33} E_{11} \u03b5_{33} \u03bd_{13} \u03bd_{31} \u03c3_{11} \u03c3_{33}")
Eq1 = Eq(e33, s33/E33)
print(Eq1)
Eq1 = Eq1.subs({e33:0.002, s33:1})
print(Eq1)
sol = solve(Eq1, E33)
print(Eq(E33, sol[0]))
Eq2 = Eq(e33, -v13*s11/E11)
print(Eq2)
Eq2 = Eq2.subs({e33:-0.0005, s11:1, E11:100})
print(Eq2)
sol = solve(Eq2, v13)
print(Eq(v13, sol[0]))
Eq3 = Eq(v13/E11, v31/E33)
print(Eq3)
Eq3 = Eq3.subs({v13:0.05, E33:500, E11:100})
print(Eq3)
sol = solve(Eq3, v31)
print(Eq(v31, sol[0]))