Home›Calculus 3›Divergence and curl›Problem 12.99

Divergence and curl

Problem 12.99 · easy

Find the divergence and curl of \( \displaystyle \mathbf{F} = \langle 2 x z, 3 \cos{\left(z \right)}, 2 y^{2} \rangle \).

\[ \frac{d}{d z} 2 y^{2} + \frac{\partial}{\partial x} 2 x z + \frac{d}{d y} 3 \cos{\left(z \right)} = 2 z \]
div F.✓ Proved
\[ \left[\begin{matrix}\frac{d}{d y} 2 y^{2} - \frac{d}{d z} 3 \cos{\left(z \right)}\\- \frac{d}{d x} 2 y^{2} + \frac{\partial}{\partial z} 2 x z\\- \frac{\partial}{\partial y} 2 x z + \frac{d}{d x} 3 \cos{\left(z \right)}\end{matrix}\right] = \left[\begin{matrix}4 y + 3 \sin{\left(z \right)}\\2 x\\0\end{matrix}\right] \]
curl F, component by component.✓ Proved

Answer \( \nabla\cdot\mathbf{F} = 2 z,\quad \nabla\times\mathbf{F} = \langle 4 y + 3 \sin{\left(z \right)}, 2 x, 0 \rangle \)

✓ Nihil obstat Every line of this solution was proved by the computer algebra system SymPy. The answer was also checked a second way, without looking at the solution. Reviewers found nothing wrong with the explanation. How we verify

The full receipt

Line	Status	Checked by	Detail
1	✓ Proved	sympy 1.14.0	simplify(lhs - rhs) reduced to 0
2	✓ Proved	sympy 1.14.0	simplify(lhs - rhs) reduced to 0
answer, a second way	✓ Checked independently	sympy 1.14.0 + mpmath 1.3.0	difference quotients of each component at (0.3, 0.7, 1.1) agree

Reviewers

gpt-oss:20b: pass
qwen3.6:27b-mlx: pass — The solution correctly computes the divergence and curl using the standard definitions. The algebraic steps are verified as correct, and the final result matches the stated answer.

Every verdict on record (6)

qwen3.6:27b-mlx: pass 2026-09-28 — The solution correctly computes the divergence and curl using the standard definitions. The algebraic steps are verified as correct, and the final result matches the stated answer.
gpt-oss:20b: pass 2026-09-28
qwen3.6:27b-mlx: pass 2026-09-26 — The solution correctly computes the divergence and curl using standard formulas. The algebraic results are verified as correct.
gpt-oss:20b: pass 2026-09-26
qwen3.6:27b-mlx: pass 2026-09-26 — The solution correctly computes the divergence and curl of the given vector field. The intermediate steps and final results are mathematically sound.
gpt-oss:20b: pass 2026-09-26

Proved: SymPy reduced the difference between the two sides to zero. Checked independently: a separate method, named above, confirmed it. Checked numerically: the two sides agree at every sampled point, which is evidence, not proof. Reviewed: a model or a person read it; that is all a sentence can have. Solution by generator:structured/divergence_curl, checked 2026-09-28 with SymPy 1.14.0.