Limit of \( \displaystyle \frac{e^{4 x - 2} - 1}{\sin{\left(2 x - 1 \right)}} \) as \( x \to \frac{1}{2} \)
Problem 1.313 · medium
Evaluate \( \displaystyle \lim_{x \to \frac{1}{2}} \frac{e^{4 x - 2} - 1}{\sin{\left(2 x - 1 \right)}} \).
- \[ \lim_{x \to \frac{1}{2}^+}\left(\frac{e^{4 x - 2} - 1}{\sin{\left(2 x - 1 \right)}}\right) \]limitStart with the original limit.✓ Proved
- \[ = \lim_{x \to \frac{1}{2}^+}\left(\frac{\frac{d}{d x} \left(e^{4 x - 2} - 1\right)}{\frac{d}{d x} \sin{\left(2 x - 1 \right)}}\right) \]lhopitalApply L'Hopital's rule because the limit is of the form 0/0.✓ Proved
- \[ = \lim_{x \to \frac{1}{2}^+}\left(\frac{2 e^{4 x - 2}}{\cos{\left(2 x - 1 \right)}}\right) \]simplify simplifyCompute the derivatives. Simplify the fraction by dividing by 2.✓ Proved
- \[ = \lim_{x \to \frac{1}{2}^+} 2 \]limit simplify simplifyEvaluate the limit by substituting x = 1/2. Simplify the exponents and trigonometric arguments. Evaluate the exponential and cosine functions.✓ Proved
- \[ = 2 \]simplifyFinal result.✓ Proved
Answer \( 2 \)
✓ 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
| Line | Status | Checked by | Detail |
|---|---|---|---|
| 1 | ✓ Proved | sympy 1.14.0 | line 1 is the problem as stated |
| 2 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where sin(2*x - 1) = 0 undefined where Derivative(sin(2*x - 1), x) = 0 |
| 3 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where Derivative(sin(2*x - 1), x) = 0 undefined where cos(2*x - 1) = 0 |
| 4 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where cos(2*x - 1) = 0 |
| 5 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where cos(2*x - 1) = 0 |
| 6 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 |
| 7 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 |
| 8 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 |
| answer | ✓ Proved | sympy 1.14.0 | final line against the stated answer: simplify(a - b) reduced to 0 |
| answer, a second way | ✓ Proved | sympy 1.14.0 | SymPy took the limit from both sides and got the stated value |
Reviewers
gpt-oss:20b: passqwen3.6:27b-mlx: pass
Every verdict on record (4)
gpt-oss:20b: pass 2026-10-06qwen3.6:27b-mlx: pass 2026-10-06qwen3.6:27b-mlx: pass 2026-10-06gpt-oss:20b: pass 2026-10-06
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 2026-10-06 with SymPy 1.14.0.