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The solution to this is probably easy, but I haven't been able to find it. Using SymPy, I am trying to solve this equation: $$ {x_1}^2 + {x_2}^2 + {x_3}^2 + 3 = a $$ with this constraint: $$ ...
#2: Post edited
by
wjandrea
·
2026-07-10T08:03:39Z (2 months ago)
Clarify math notation (at first it looked like `x**(2/3)` e.g.). Capitalization.
how to apply a unit constraint in Sympy
- How to apply a unit constraint in SymPy
- The solution to this is probably easy, but I haven't been able to find it.
Using Sympy, I am trying to solve this equation:- $$
x_1^2 + x_2^2 + x_3^2 + 3 = a- $$
- with this constraint:
- $$
x_1^2 + x_2^2 + x_3^2 = 1- $$
- It is obvious that $a=4$. So, I wrote this code:
- ```python
- import sympy as sp
- a, x1, x2, x3 = sp.symbols('a x1 x2 x3')
- eq1 = x1**2 + x2**2 + x3**2 + 3 - a
- eq2 = x1**2 + x2**2 + x3**2 - 1
- sol = sp.solve([eq1, eq2], a)
- print(sol)
- ```
- Which returns:
- ```
- {a: x1**2 + x2**2 + x3**2 + 3}
- ```
- The unit-norm constraint on `x` is not applied.
How can I get Sympy to apply the unit-norm constraint, which results in $a=4$?
- The solution to this is probably easy, but I haven't been able to find it.
- Using SymPy, I am trying to solve this equation:
- $$
- {x_1}^2 + {x_2}^2 + {x_3}^2 + 3 = a
- $$
- with this constraint:
- $$
- {x_1}^2 + {x_2}^2 + {x_3}^2 = 1
- $$
- It is obvious that $a=4$. So, I wrote this code:
- ```python
- import sympy as sp
- a, x1, x2, x3 = sp.symbols('a x1 x2 x3')
- eq1 = x1**2 + x2**2 + x3**2 + 3 - a
- eq2 = x1**2 + x2**2 + x3**2 - 1
- sol = sp.solve([eq1, eq2], a)
- print(sol)
- ```
- Which returns:
- ```
- {a: x1**2 + x2**2 + x3**2 + 3}
- ```
- The unit-norm constraint on `x` is not applied.
- How can I get SymPy to apply the unit-norm constraint, which results in $a=4$?
#1: Initial revision
by
Trevor
·
2026-07-07T06:19:30Z (2 months ago)
how to apply a unit constraint in Sympy
The solution to this is probably easy, but I haven't been able to find it.
Using Sympy, I am trying to solve this equation:
$$
x_1^2 + x_2^2 + x_3^2 + 3 = a
$$
with this constraint:
$$
x_1^2 + x_2^2 + x_3^2 = 1
$$
It is obvious that $a=4$. So, I wrote this code:
```python
import sympy as sp
a, x1, x2, x3 = sp.symbols('a x1 x2 x3')
eq1 = x1**2 + x2**2 + x3**2 + 3 - a
eq2 = x1**2 + x2**2 + x3**2 - 1
sol = sp.solve([eq1, eq2], a)
print(sol)
```
Which returns:
```
{a: x1**2 + x2**2 + x3**2 + 3}
```
The unit-norm constraint on `x` is not applied.
How can I get Sympy to apply the unit-norm constraint, which results in $a=4$?