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Derivative of \( \displaystyle \frac{3 \ln{\left(\tan^{2}{\left(5 x - 3 \right)} + 1 \right)}}{10} \)

Problem 2.168 · hard

Differentiate \( \displaystyle f(x) = \frac{3 \ln{\left(\tan^{2}{\left(5 x - 3 \right)} + 1 \right)}}{10} \).
  1. \[ \frac{d}{d x} \frac{3 \ln{\left(\tan^{2}{\left(5 x - 3 \right)} + 1 \right)}}{10} \]
    derivativeStart with the derivative of the function.✓ Proved
  2. \[ = \frac{3 \frac{d}{d x} \ln{\left(\tan^{2}{\left(5 x - 3 \right)} + 1 \right)}}{10} \]
    constant-multiplePull out the constant factor.✓ Proved
  3. \[ = \frac{3 \frac{d}{d x} \left(\tan^{2}{\left(5 x - 3 \right)} + 1\right)}{10 \left(\tan^{2}{\left(5 x - 3 \right)} + 1\right)} \]
    logarithmicApply the chain rule for the logarithm.✓ Proved
  4. \[ = \frac{3 \left(\frac{d}{d x} 1 + \frac{d}{d x} \tan^{2}{\left(5 x - 3 \right)}\right)}{10 \left(\tan^{2}{\left(5 x - 3 \right)} + 1\right)} \]
    sumDifferentiate the sum inside the parentheses.✓ Proved
  5. \[ = \frac{3 \frac{d}{d x} \tan^{2}{\left(5 x - 3 \right)}}{10 \left(\tan^{2}{\left(5 x - 3 \right)} + 1\right)} \]
    constantThe derivative of a constant is zero.✓ Proved
  6. \[ = \frac{3 \tan{\left(5 x - 3 \right)} \frac{d}{d x} \tan{\left(5 x - 3 \right)}}{5 \left(\tan^{2}{\left(5 x - 3 \right)} + 1\right)} \]
    powerApply the power rule to the squared term.✓ Proved
  7. \[ = \frac{3 \tan{\left(5 x - 3 \right)} \sec^{2}{\left(5 x - 3 \right)} \frac{d}{d x} \left(5 x - 3\right)}{5 \left(\tan^{2}{\left(5 x - 3 \right)} + 1\right)} \]
    trigApply the chain rule for the tangent function.≈ Checked numerically
  8. \[ = \frac{3 \tan{\left(5 x - 3 \right)} \sec^{2}{\left(5 x - 3 \right)}}{\tan^{2}{\left(5 x - 3 \right)} + 1} \]
    derivative algebra simplifyDifferentiate the innermost linear expression. Multiply the constants. Simplify the expression by canceling 10.✓ Proved
  9. \[ = 3 \tan{\left(5 x - 3 \right)} \]
    rewrite simplifyUse the identity sec(u)**2 = 1 + tan(u)**2. Cancel the common factor (tan(5*x - 3)**2 + 1).≈ Checked numerically
Answer \( 3 \tan{\left(5 x - 3 \right)} \)
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 Lines: 11 proved, 2 checked numerically. 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
log is undefined for non-positive arguments
tan has poles at odd multiples of pi/2
3✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
tan has poles at odd multiples of pi/2
undefined where tan(5*x - 3)**2 + 1 = 0
4✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
tan has poles at odd multiples of pi/2
undefined where tan(5*x - 3)**2 + 1 = 0
5✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
tan has poles at odd multiples of pi/2
undefined where tan(5*x - 3)**2 + 1 = 0
6✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
tan has poles at odd multiples of pi/2
undefined where tan(5*x - 3)**2 + 1 = 0
7≈ Checked numericallysympy 1.14.0sympy 1.14.0: simplify left 3*(tan(5*x - 3)**2 - sec(5*x - 3)**2 + 1)*tan(5*x - 3)/(tan(5*x - 3)**2 + 1); numeric agreement only, at 24 of 24 sampled points
tan has poles at odd multiples of pi/2
undefined where tan(5*x - 3)**2 + 1 = 0
sec has poles at odd multiples of pi/2
8✓ 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
undefined where tan(5*x - 3)**2 + 1 = 0
9✓ 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
undefined where tan(5*x - 3)**2 + 1 = 0
10✓ 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
undefined where tan(5*x - 3)**2 + 1 = 0
11≈ Checked numericallysympy 1.14.0sympy 1.14.0: simplify left 3*(-tan(5*x - 3)**2 + sec(5*x - 3)**2 - 1)*tan(5*x - 3)/(tan(5*x - 3)**2 + 1); numeric agreement only, at 24 of 24 sampled points
tan has poles at odd multiples of pi/2
sec has poles at odd multiples of pi/2
undefined where tan(5*x - 3)**2 + 1 = 0
12✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
tan 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: pass
  • qwen3.6:27b-mlx: pass
Every verdict on record (15)
  • qwen3.6:27b-mlx: pass 2026-09-20
  • gpt-oss:20b: pass 2026-09-20
  • qwen3.6:27b-mlx: pass 2026-09-20
  • gpt-oss:20b: pass 2026-09-20
  • qwen3.6:27b-mlx: pass 2026-09-19
  • deepseek-r1:70b: pass 2026-09-19
  • gpt-oss:20b: pass 2026-09-19
  • qwen3.6:27b-mlx: pass 2026-09-19 — The solution correctly applies differentiation rules step-by-step, adhering to the one-change-per-step constraint. The labels used are appropriate for the operations performed, and the final simplification is mathematically sound.
  • deepseek-r1:70b: pass 2026-09-19
  • gpt-oss:20b: pass 2026-09-19
  • qwen3.6:27b-mlx: pass 2026-09-18
  • deepseek-r1:70b: pass 2026-09-18
  • gpt-oss:20b: pass 2026-09-18
  • gpt-oss:20b: pass 2026-09-17
  • 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.