Integral of \( \displaystyle \frac{\sin{\left(x \right)}}{\cos^{2}{\left(x \right)}} \)
Problem 4.181 · medium
Find \( \displaystyle \int \frac{\sin{\left(x \right)}}{\cos^{2}{\left(x \right)}} \, dx \). (Omit the constant of integration.)
- \[ \int \frac{\sin{\left(x \right)}}{\cos^{2}{\left(x \right)}}\, dx \]integral algebraStart with the integral of the given function. Rewrite the fraction as a product.✓ Proved
- \[ = \int \sin{\left(x \right)} \sec^{2}{\left(x \right)}\, dx \]rewriteUse the identity 1/cos(x)**2 = sec(x)**2.✓ Proved
- \[ = \int \tan{\left(x \right)} \sec{\left(x \right)}\, dx \]rewriteUse the identity sin(x)/cos(x) = tan(x).✓ Proved
- \[ = \sec{\left(x \right)} \]antiderivativeThe antiderivative of sec(x)tan(x) is sec(x).✓ Proved
Answer \( \frac{1}{\cos{\left(x \right)}} + C \)
✓ 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 cos(x) = 0 |
| 3 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where cos(x) = 0 sec has poles at odd multiples of pi/2 |
| 4 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 sec has poles at odd multiples of pi/2 tan has poles at odd multiples of pi/2 |
| 5 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 tan has poles at odd multiples of pi/2 sec has poles at odd multiples of pi/2 |
| answer | ✓ Proved | sympy 1.14.0 | final line against the stated answer: simplify(a - b) reduced to 0 undefined where cos(x) = 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 2026-09-29gpt-oss:20b: pass 2026-09-29qwen3.6:27b-mlx: pass 2026-09-29gpt-oss:20b: pass 2026-09-29
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 2026-09-29 with SymPy 1.14.0.