∫Calc Practice
Home›Calculus 1›Power rule›Problem 2.47

Derivative of \( \displaystyle \sqrt{x^{2} + 1} \)

Problem 2.47 · easy

Differentiate \( \displaystyle f(x) = \sqrt{x^{2} + 1} \).
  1. \[ \frac{d}{d x} \sqrt{x^{2} + 1} \]
    derivative rewriteStart with the derivative of the function. Rewrite the square root as a fractional exponent.✓ Proved
  2. \[ = \frac{\frac{d}{d x} \left(x^{2} + 1\right)}{2 \sqrt{x^{2} + 1}} \]
    chainApply the chain rule.✓ Proved
  3. \[ = \frac{x}{\sqrt{x^{2} + 1}} \]
    derivative algebra simplifyDifferentiate the inner function. Simplify the expression by canceling the 2. Rewrite with a positive exponent.✓ Proved
Answer \( \frac{x}{\sqrt{x^{2} + 1}} \)

✓ 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
3✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where x**2 + 1 = 0
4✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where x**2 + 1 = 0
5✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where x**2 + 1 = 0
6✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where x**2 + 1 = 0
answer✓ Provedsympy 1.14.0final line against the stated answer: simplify(a - b) reduced to 0
undefined where x**2 + 1 = 0
answer, a second way✓ Provedsympy 1.14.0SymPy differentiated f directly and got the stated answer

Reviewers

  • gpt-oss:20b: pass
  • deepseek-r1:70b: pass
  • qwen3.6:27b-mlx: pass
Every verdict on record (12)
  • qwen3.6:27b-mlx: pass 2026-09-20
  • gpt-oss:20b: pass 2026-09-20
  • qwen3.6:27b-mlx: pass 2026-09-20
  • gpt-oss:20b: pass 2026-09-20
  • qwen3.6:27b-mlx: pass 2026-09-19
  • deepseek-r1:70b: pass 2026-09-19
  • gpt-oss:20b: pass 2026-09-19
  • qwen3.6:27b-mlx: pass 2026-09-19
  • deepseek-r1:70b: pass 2026-09-19
  • gpt-oss:20b: pass 2026-09-19
  • gpt-oss:20b: pass 2026-09-17
  • deepseek-r1:70b: pass 2026-09-17

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 2026-09-26 with SymPy 1.14.0.