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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.)
  1. \[ \int \frac{\sin{\left(x \right)}}{\cos^{2}{\left(x \right)}}\, dx \]
    integral algebraStart with the integral of the given function. Rewrite the fraction as a product.✓ Proved
  2. \[ = \int \sin{\left(x \right)} \sec^{2}{\left(x \right)}\, dx \]
    rewriteUse the identity 1/cos(x)**2 = sec(x)**2.✓ Proved
  3. \[ = \int \tan{\left(x \right)} \sec{\left(x \right)}\, dx \]
    rewriteUse the identity sin(x)/cos(x) = tan(x).✓ Proved
  4. \[ = \sec{\left(x \right)} \]
    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
LineStatusChecked byDetail
1✓ Provedsympy 1.14.0line 1 is the problem as stated
2✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where cos(x) = 0
3✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where cos(x) = 0
sec has poles at odd multiples of pi/2
4✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
sec has poles at odd multiples of pi/2
tan has poles at odd multiples of pi/2
5✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
tan has poles at odd multiples of pi/2
sec has poles at odd multiples of pi/2
answer✓ Provedsympy 1.14.0final line against the stated answer: simplify(a - b) reduced to 0
undefined where cos(x) = 0
answer, a second way✓ Provedsympy 1.14.0SymPy differentiated the stated antiderivative back to the integrand

Reviewers

  • gpt-oss:20b: pass
  • qwen3.6:27b-mlx: pass
Every verdict on record (4)
  • qwen3.6:27b-mlx: pass 2026-09-29
  • gpt-oss:20b: pass 2026-09-29
  • qwen3.6:27b-mlx: pass 2026-09-29
  • gpt-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.