Derivative of \( \displaystyle \operatorname{asin}{\left(2 x + 1 \right)} \)
Problem 2.1678 · medium
Differentiate \( \displaystyle f(x) = \operatorname{asin}{\left(2 x + 1 \right)} \).
- \[ \frac{d}{d x} \operatorname{asin}{\left(2 x + 1 \right)} \]derivativeStart with the derivative of the function.✓ Proved
- \[ = \frac{\frac{d}{d x} \left(2 x + 1\right)}{\sqrt{1 - \left(2 x + 1\right)^{2}}} \]chainApply the chain rule for the arcsine function.✓ Proved
- \[ = \frac{2}{\sqrt{1 - \left(2 x + 1\right)^{2}}} \]derivative algebraDifferentiate the inner function 2*x + 1. Multiply the terms.✓ Proved
- \[ = \frac{2}{\sqrt{- 4 x^{2} - 4 x}} \]algebra simplifyExpand the square inside the square root. Simplify the expression inside the square root.✓ Proved
- \[ = \frac{1}{\sqrt{- x^{2} - x}} \]algebra simplifyFactor out 4 from the expression inside the square root. Simplify the fraction.✓ Proved
Answer \( \frac{1}{\sqrt{x \left(- x - 1\right)}} \)
✓ 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 asin is real only on [-1, 1] undefined where 1 - (2*x + 1)**2 = 0 |
| 3 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where 1 - (2*x + 1)**2 = 0 |
| 4 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where 1 - (2*x + 1)**2 = 0 |
| 5 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where 1 - (2*x + 1)**2 = 0 undefined where -4*x**2 - 4*x = 0 |
| 6 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where -4*x**2 - 4*x = 0 |
| 7 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where -4*x**2 - 4*x = 0 undefined where -x**2 - x = 0 |
| 8 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where -x**2 - x = 0 |
| answer | ✓ Proved | sympy 1.14.0 | final line against the stated answer: simplify(a - b) reduced to 0 undefined where x*(-x - 1) = 0 |
| answer, a second way | ✓ Proved | sympy 1.14.0 | SymPy differentiated f directly and got the stated answer |
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 2026-10-06gpt-oss:20b: pass 2026-10-06qwen3.6:27b-mlx: 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.