Limit of \( \displaystyle \frac{1 - \cos{\left(x \right)}}{x^{2}} \) as \( x \to 0 \)
Problem 1.305 · easy
Evaluate \( \displaystyle \lim_{x \to 0} \frac{1 - \cos{\left(x \right)}}{x^{2}} \).
- \[ \lim_{x \to 0^+}\left(\frac{1 - \cos{\left(x \right)}}{x^{2}}\right) \]limitIdentify the limit to be evaluated.✓ Proved
- \[ = \lim_{x \to 0^+}\left(\frac{\frac{d}{d x} \left(1 - \cos{\left(x \right)}\right)}{\frac{d}{d x} x^{2}}\right) \]lhopitalApply L'Hopital's rule because the limit is of the form 0/0.✓ Proved
- \[ = \lim_{x \to 0^+}\left(\frac{\sin{\left(x \right)}}{2 x}\right) \]simplifyDifferentiate the numerator and denominator.✓ Proved
- \[ = \lim_{x \to 0^+}\left(\frac{\sin{\left(x \right)}}{x}\right) \lim_{x \to 0^+} \frac{1}{2} \]limit-lawSeparate the constant factor from the limit.✓ Proved
- \[ = \frac{\lim_{x \to 0^+}\left(\frac{\sin{\left(x \right)}}{x}\right)}{2} \]simplifyEvaluate the constant factor.✓ Proved
- \[ = \frac{\lim_{x \to 0^+}\left(\frac{\frac{d}{d x} \sin{\left(x \right)}}{\frac{d}{d x} x}\right)}{2} \]lhopitalApply L'Hopital's rule to the remaining indeterminate form.✓ Proved
- \[ = \frac{\lim_{x \to 0^+} \cos{\left(x \right)}}{2} \]simplify limit-lawDifferentiate the numerator and denominator. Apply the limit to the function part.✓ Proved
- \[ = \frac{1}{2} \]limit simplifyEvaluate the limit of cos(x) at 0. Final result.✓ Proved
Answer \( \frac{1}{2} \)
✓ 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 x = 0 undefined where Derivative(x**2, x) = 0 |
| 3 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where Derivative(x**2, x) = 0 undefined where x = 0 |
| 4 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where x = 0 |
| 5 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where x = 0 |
| 6 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where x = 0 undefined where Derivative(x, x) = 0 |
| 7 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where Derivative(x, x) = 0 |
| 8 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 |
| 9 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 |
| 10 | ✓ 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 — The solution correctly applies L'Hopital's rule twice, with appropriate simplification and limit laws at each stage. Each step changes only one aspect of the expression and uses valid labels from the fixed vocabulary.
Every verdict on record (4)
gpt-oss:20b: pass 2026-10-06qwen3.6:27b-mlx: pass 2026-10-06 — The solution correctly applies L'Hopital's rule twice, with appropriate simplification and limit laws at each stage. Each step changes only one aspect of the expression and uses valid labels from the fixed vocabulary.qwen3.6:27b-mlx: pass 2026-10-06 — The solution correctly applies L'Hopital's rule and limit laws. Each step changes only one aspect of the expression, and the labels accurately reflect the operations performed.gpt-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.