Integral of \( \displaystyle 2 x \sin{\left(2 x \right)} \)
Problem 4.883 · medium
Find \( \displaystyle \int 2 x \sin{\left(2 x \right)} \, dx \). (Omit the constant of integration.)
- \[ \int 2 x \sin{\left(2 x \right)}\, dx \]integralStart with the integral of the function.✓ Proved
- \[ = \operatorname{parts}{\left(2 x \sin{\left(2 x \right)},x,1,\sin{\left(2 x \right)},- \frac{\cos{\left(2 x \right)}}{2} \right)} \]partsApply integration by parts where u = 2*x and dv = sin(2*x)dx.Reviewed
- \[ = - x \cos{\left(2 x \right)} - \int \left(- \cos{\left(2 x \right)}\right)\, dx \]partsApply the integration by parts formula: integral(u dv) = u v - integral(v du).Reviewed
- \[ = - x \cos{\left(2 x \right)} + \int \cos{\left(2 x \right)}\, dx \]simplifySimplify the expression inside and outside the integral.✓ Proved
- \[ = - x \cos{\left(2 x \right)} + \frac{\sin{\left(2 x \right)}}{2} \]antiderivativeEvaluate the remaining integral.✓ Proved
Answer \( - x \cos{\left(2 x \right)} + \frac{\sin{\left(2 x \right)}}{2} + C \)
Lines: 4 proved, 2 reviewed. 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 | Reviewed | reviewers: gpt-oss:20b, qwen3.6:27b-mlx | simplify left -x*cos(2*x) - parts(2*x*sin(2*x), x, 1, sin(2*x), -cos(2*x)/2) + sin(2*x)/2; no point in the sample was defined on both lines |
| 3 | Reviewed | reviewers: gpt-oss:20b, qwen3.6:27b-mlx | simplify left x*cos(2*x) + parts(2*x*sin(2*x), x, 1, sin(2*x), -cos(2*x)/2) - sin(2*x)/2; no point in the sample was defined on both lines |
| 4 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 |
| 5 | ✓ 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 differentiated the stated antiderivative back to the integrand |
Reviewers
gpt-oss:20b: passqwen3.6:27b-mlx: pass
Every verdict on record (4)
qwen3.6:27b-mlx: pass 2026-10-11gpt-oss:20b: pass 2026-10-11qwen3.6:27b-mlx: pass 2026-10-11gpt-oss:20b: pass 2026-10-11
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 2026-10-11 with SymPy 1.14.0.