∫Calc Practice

Limit of \( \displaystyle \frac{\tan{\left(2 x - 1 \right)}}{2 x - 1} \) as \( x \to \frac{1}{2} \)

Problem 1.356 · medium

Evaluate \( \displaystyle \lim_{x \to \frac{1}{2}} \frac{\tan{\left(2 x - 1 \right)}}{2 x - 1} \).
  1. \[ \lim_{x \to \frac{1}{2}^+}\left(\frac{\tan{\left(2 x - 1 \right)}}{2 x - 1}\right) \]
    limitStart with the original limit.✓ Proved
  2. \[ = \lim_{u \to 0^+}\left(\frac{\tan{\left(u \right)}}{u}\right) \]
    substitutionLet u = 2*x - 1. As x approaches 1/2, u approaches 0.✓ Proved
  3. \[ = \lim_{u \to 0^+}\left(\frac{\frac{d}{d u} \tan{\left(u \right)}}{\frac{d}{d u} u}\right) \]
    lhopitalApply L'Hopital's Rule since the limit is in the form 0/0.✓ Proved
  4. \[ = \lim_{u \to 0^+} \sec^{2}{\left(u \right)} \]
    simplifyCompute the derivatives of the numerator and denominator.✓ Proved
  5. \[ = 1 \]
    limit simplifyEvaluate the limit by plugging in u = 0. Simplify the final value.✓ Proved
Answer \( 1 \)

✓ 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.

The full receipt
LineStatusChecked byDetail
1✓ Provedsympy 1.14.0line 1 is the problem as stated
2✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
tan has poles at odd multiples of pi/2
undefined where 2*x - 1 = 0
undefined where u = 0
3✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
tan has poles at odd multiples of pi/2
undefined where u = 0
undefined where Derivative(u, u) = 0
4✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
tan has poles at odd multiples of pi/2
undefined where Derivative(u, u) = 0
sec has poles at odd multiples of pi/2
5✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
sec has poles at odd multiples of pi/2
6✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
answer✓ Provedsympy 1.14.0final line against the stated answer: simplify(a - b) reduced to 0
answer, a second way✓ Provedsympy 1.14.0SymPy took the limit from both sides and got the stated value

Reviewers

  • gpt-oss:20b: pass
  • qwen3.6:27b-mlx: pass
Every verdict on record (4)
  • gpt-oss:20b: pass 2026-10-07
  • qwen3.6:27b-mlx: pass 2026-10-07
  • qwen3.6:27b-mlx: pass 2026-10-07 — The solution correctly applies substitution, L'Hopital's rule, and evaluation. Each step changes only one aspect of the expression and uses valid labels from the fixed vocabulary.
  • gpt-oss:20b: pass 2026-10-07

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 gemma4:26b, checked 2026-10-07 with SymPy 1.14.0.