∫Calc Practice

Derivative of \( \displaystyle \tan{\left(x \right)} \)

Problem 2.36 · easy

Differentiate \( \displaystyle f(x) = \tan{\left(x \right)} \).
  1. \[ \frac{d}{d x} \tan{\left(x \right)} \]
    derivativeStart with the derivative of the function.✓ Proved
  2. \[ = \frac{d}{d x} \frac{\sin{\left(x \right)}}{\cos{\left(x \right)}} \]
    rewrite productRewrite tan(x) as sin(x)/cos(x). Rewrite the quotient as a product.✓ Proved
  3. \[ = \sin{\left(x \right)} \frac{d}{d x} \frac{1}{\cos{\left(x \right)}} + \frac{\frac{d}{d x} \sin{\left(x \right)}}{\cos{\left(x \right)}} \]
    productApply the product rule.✓ Proved
  4. \[ = \sin{\left(x \right)} \frac{d}{d x} \frac{1}{\cos{\left(x \right)}} + 1 \]
    derivative rewriteDifferentiate sin(x). Rewrite 1/cos(x) as cos(x)**(-1).✓ Proved
  5. \[ = - \frac{\sin{\left(x \right)} \frac{d}{d x} \cos{\left(x \right)}}{\cos^{2}{\left(x \right)}} + 1 \]
    chainApply the chain rule to cos(x)**(-1).✓ Proved
  6. \[ = \frac{\sin^{2}{\left(x \right)}}{\cos^{2}{\left(x \right)}} + 1 \]
    derivative algebra algebra algebra algebraDifferentiate cos(x). Simplify the signs and terms. Rearrange the terms. Rewrite the negative exponent. Combine the fraction.✓ Proved
  7. \[ = \tan^{2}{\left(x \right)} + 1 \]
    rewriteRewrite the fraction as tan(x).✓ Proved
  8. \[ = \sec^{2}{\left(x \right)} \]
    simplifyUse the trigonometric identity 1 + tan(x)**2 = sec(x)**2.✓ Proved
Answer \( \tan^{2}{\left(x \right)} + 1 \)
Mind the domain. The answer is also defined at points where f(x) is not. Substituting there gives a number that is not a slope of f.

✓ 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
tan has poles at odd multiples of pi/2
undefined where cos(x) = 0
3✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where cos(x) = 0
4✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where cos(x) = 0
5✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where cos(x) = 0
6✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where cos(x) = 0
7✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where cos(x) = 0
8✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where cos(x) = 0
9✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where cos(x) = 0
10✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where cos(x) = 0
11✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where cos(x) = 0
12✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where cos(x) = 0
13✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where cos(x) = 0
tan has poles at odd multiples of pi/2
14✓ 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
tan has poles at odd multiples of pi/2
answer, a second way✓ Provedsympy 1.14.0SymPy differentiated f directly and got the stated answer

Reviewers

  • gpt-oss:20b: pass
  • deepseek-r1:70b: fail (style) — Step 3 mislabels a rewrite as a product rule.
  • qwen3.6:27b-mlx: fail (style) — Step 3 applies two rules at once: it rewrites 1/cos(x) as a product factor and implicitly prepares for the product rule, but the label 'product' is incorrect for a rewriting step that does not yet apply the differentiation rule. The step should be labeled 'rewrite' or split into a rewrite step followed by a product rule step.
Every verdict on record (12)
  • qwen3.6:27b-mlx: fail (style) 2026-09-20 — Step 3 applies two rules at once: it rewrites 1/cos(x) as a product factor and implicitly prepares for the product rule, but the label 'product' is incorrect for a rewriting step that does not yet apply the differentiation rule. The step should be labeled 'rewrite' or split into a rewrite step followed by a product rule step.
  • gpt-oss:20b: pass 2026-09-20
  • qwen3.6:27b-mlx: pass 2026-09-20 — The solution correctly applies the product rule, chain rule, and trigonometric identities in distinct steps. The final simplification to sec(x)**2 is a valid equivalent form, even though the stated answer was tan(x)**2 + 1.
  • gpt-oss:20b: pass 2026-09-20
  • qwen3.6:27b-mlx: pass 2026-09-19 — The solution correctly applies the product rule and chain rule in separate steps, adhering to the one-change-per-step constraint. The labels accurately reflect the operations performed.
  • deepseek-r1:70b: fail (style) 2026-09-19 — Step 3 mislabels a rewrite as a product rule.
  • 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: fail 2026-09-17 — Step 3 incorrectly labels the operation as a product rule; it is merely a rewrite of sin(x)/cos(x) into sin(x)*(1/cos(x)).
  • 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.