solving nonlinear system

Question

I write this code to solve eight equations. But this error is exhibited.
"can't convert expression to float"
What is the problem?

import sympy as sym
from sympy.solvers import solve
import numpy as np
from math import log
from math import sqrt
from math import cos
T=-22
L=23.39
D0=0.266475941
D100=0.255457305
D200=0.229910814
D300=0.199324382
D450=0.15539571
D600=0.119089308
D900=0.070524324
D1200=0.043925175
sym.init_printing()
a,b,c,d,j,f,g,h=sym.symbols('a,b,c,d,j,f,g,h')
A=sym.Eq(0.062015383726393*T*L/(c + g*a) + 2.50461005642387*L/(b + g + 0.00150093890629873*d*j + 0.00150093890629873*d*g - (h**0.5)),D0)
B=sym.Eq(2.51685653969386*L/(b + j) + 0.0294709874154182*T*L/(c + g) + (0.301991375261666*h + 0.486445651805026*T*L)/(d*g) - 0.0425080517681347,D100)
C=sym.Eq((1.63757186584073*T + 3.30124351745675*log(h) + 0.952978463603516*a*log(h) - 0.22574369565679*d)/(b + j + 0.115826919448799*c + g*log(T + b)),D200)
D=sym.Eq(1.42041574752534*a/(g + 0.640226710296927*b + 0.193086683763814*d) + (495 + 0.745975457073521*T*a)/(j*g + 0.0207514715201547*d*c + b*sqrt(g)),D300)
J=sym.Eq(7.60657578727923/c + 0.0190340589524935*a**2/(g + 0.460411094180136*b) + (0.460411094180136*h + 1.25627439526128*T*a)/(46.5721463433838*j + d*g),D450)
F=sym.Eq((0.678699415617512*L*h + 0.104253726575244*T*h)/(21.0226270392147*d + d*j + d*g + h*g + 0.112737474380886*b*c + 0.112737474380886*b*h),D600)
G=sym.Eq((L + 0.062444236690004*L*sqrt(h))/(b + j + 2.46016390558638*g + g*d**0.341389457034226 - 0.0123838604808271*T*b),D900)
H=sym.Eq(0.0201527324507928*T + 0.00533320842635642*L*sqrt(h))/(g + 0.0654908487489791*j + 0.000128770004806114*b*d + cos(-0.0101921210626875*f),D1200)

print(sym.solve([A,B,C,D,J,F,G,H],(a,b,c,d,j,f,g,h)))

Answer 1

HI Fatemeh Hoseini! Avoid put floats directly inside the equations. Put them in variables or a tuple. Then your cide vill be more readable. And use more parentheses were there can be ambiguities.

Just as an example:

. . .
constA = (
0.062015383726393,
2.50461005642387,
0.00150093890629873,
0.00150093890629873
)

A = sym.Eq((constA[0] * T * L)/(c + g*a) + (constA[1] * L)/(b + g + constA[2]*d*j + constA[3]*d*g - (h**0.5)), D0)
. . .

Answer 2

It is always helpful for others if you save your code in the playground, and link to it in your question. That way people can immediately test it.

You need to fix your imports, you cannot use functions of the math library on symbolic expressions, use sympy instead

from sympy import log
from sympy import sqrt
from sympy import cos

In your last equation verify to use parentheses in the correct places. You need to pass one expression and one value to sympy.Eq()

The code runs without errors after these changes, but timeout on Sololearn

Answer 3

You don't need to create a new thread. Just post in your own thread if you want to add something.

https://www.sololearn.com/Discuss/3034980/?ref=app