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Eliminating the parameter

Problem 8.371 · medium

Eliminate the parameter from \( \displaystyle x = 2 \sec{\left(t \right)},\ y = 2 \tan{\left(t \right)} \), and say what kind of curve it is.

sec²t − tan²t = 1.
Reviewed
\[ \left. \frac{x^{2}}{4} - \frac{y^{2}}{4} - 1 \right|_{\substack{ x=2 \sec{\left(t \right)}\\ y=2 \tan{\left(t \right)} }} = 0 \]
The parametric point satisfies the equation for every t.✓ Proved

Answer \( \frac{x^{2}}{4} - \frac{y^{2}}{4} = 1\ (\text{hyperbola}) \)

✓ Nihil obstat Lines: 1 proved, 1 reviewed. 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	Reviewed	reviewers: gpt-oss:20b, qwen3.6:27b-mlx	a sentence; read, not computed
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	points on the parametric curve at four values of t satisfy the equation

Reviewers

gpt-oss:20b: pass
qwen3.6:27b-mlx: pass — The solution correctly identifies the trigonometric identity and verifies that the parametric equations satisfy the Cartesian equation of a hyperbola.

Every verdict on record (6)

qwen3.6:27b-mlx: pass 2026-10-18 — The solution correctly identifies the trigonometric identity and verifies that the parametric equations satisfy the Cartesian equation of a hyperbola.
gpt-oss:20b: pass 2026-10-18
qwen3.6:27b-mlx: pass 2026-10-16 — The solution correctly identifies the trigonometric identity and verifies that the parametric equations satisfy the resulting Cartesian equation, which is a hyperbola.
gpt-oss:20b: pass 2026-10-16
qwen3.6:27b-mlx: pass 2026-10-15 — The solution correctly identifies the trigonometric identity and verifies that the parametric equations satisfy the Cartesian equation of a hyperbola.
gpt-oss:20b: pass 2026-10-15

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/parametric_eliminate, checked 2026-10-18 with SymPy 1.14.0.