Derivative of \( \displaystyle \ln{\left(\tan{\left(5 x + 2 \right)} + \sec{\left(5 x + 2 \right)} \right)} \)
Problem 2.1076 · hard
Differentiate \( \displaystyle f(x) = \ln{\left(\tan{\left(5 x + 2 \right)} + \sec{\left(5 x + 2 \right)} \right)} \).
- \[ \frac{d}{d x} \ln{\left(\tan{\left(5 x + 2 \right)} + \sec{\left(5 x + 2 \right)} \right)} \]derivativeStart with the derivative of the function.✓ Proved
- \[ = \frac{\frac{d}{d x} \left(\tan{\left(5 x + 2 \right)} + \sec{\left(5 x + 2 \right)}\right)}{\tan{\left(5 x + 2 \right)} + \sec{\left(5 x + 2 \right)}} \]chainApply the chain rule for the natural logarithm.✓ Proved
- \[ = \frac{\frac{d}{d x} \tan{\left(5 x + 2 \right)} + \frac{d}{d x} \sec{\left(5 x + 2 \right)}}{\tan{\left(5 x + 2 \right)} + \sec{\left(5 x + 2 \right)}} \]sumApply the sum rule to the inner terms.✓ Proved
- \[ = \frac{5 \tan{\left(5 x + 2 \right)} \sec{\left(5 x + 2 \right)} + 5 \sec^{2}{\left(5 x + 2 \right)}}{\tan{\left(5 x + 2 \right)} + \sec{\left(5 x + 2 \right)}} \]chainDifferentiate the tangent and secant terms using the chain rule.≈ Checked numerically
- \[ = \frac{5 \left(\frac{\tan{\left(5 x + 2 \right)}}{\sec{\left(5 x + 2 \right)}} + 1\right) \sec^{2}{\left(5 x + 2 \right)}}{\tan{\left(5 x + 2 \right)} + \sec{\left(5 x + 2 \right)}} \]algebraFactor out common terms from the numerator.✓ Proved
- \[ = \frac{5 \tan{\left(5 x + 2 \right)} \sec{\left(5 x + 2 \right)} + 5 \sec^{2}{\left(5 x + 2 \right)}}{\tan{\left(5 x + 2 \right)} + \sec{\left(5 x + 2 \right)}} \]algebraDistribute the constant factor.✓ Proved
- \[ = 5 \sec{\left(5 x + 2 \right)} \]algebra simplifyFactor out sec(5*x + 2) from the numerator. Cancel the common term in the numerator and denominator.✓ Proved
Answer \( \frac{5}{\cos{\left(5 x + 2 \right)}} \)
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.
Lines: 8 proved, 1 checked numerically. The answer was also checked a second way, without looking at the solution. The reviewers disagree about how one step is explained; every verdict is in the receipt.
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 log is undefined for non-positive arguments tan has poles at odd multiples of pi/2 sec has poles at odd multiples of pi/2 undefined where tan(5*x + 2) + sec(5*x + 2) = 0 |
| 3 | ✓ 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 undefined where tan(5*x + 2) + sec(5*x + 2) = 0 |
| 4 | ≈ Checked numerically | sympy 1.14.0 | sympy 1.14.0: simplify left 5*(tan(5*x + 2)**2 - sec(5*x + 2)**2 + 1)/(tan(5*x + 2) + sec(5*x + 2)); 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 + 2) + sec(5*x + 2) = 0 |
| 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 undefined where tan(5*x + 2) + sec(5*x + 2) = 0 undefined where sec(5*x + 2) = 0 |
| 6 | ✓ 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 undefined where tan(5*x + 2) + sec(5*x + 2) = 0 undefined where sec(5*x + 2) = 0 |
| 7 | ✓ 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 undefined where tan(5*x + 2) + sec(5*x + 2) = 0 |
| 8 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 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(5*x + 2) = 0 |
| answer, a second way | ✓ Proved | sympy 1.14.0 | SymPy differentiated f directly and got the stated answer |
Reviewers
gpt-oss:20b: passqwen3.6:27b-mlx: pass
Every verdict on record (4)
qwen3.6:27b-mlx: pass 2026-09-28gpt-oss:20b: pass 2026-09-28qwen3.6:27b-mlx: pass 2026-09-28 — The solution correctly applies the chain rule, sum rule, and standard derivatives. The algebraic simplification steps are valid and correctly labeled.gpt-oss:20b: inconclusive 2026-09-28 — reviewer response could not be parsed: {"verdict":"fail","severity":"error","notes":"The cancellation in step 8 is invalid: \n\\(\\frac{5\\,\\sec(5x+2)(\\sec(5x+2)+\\tan(5x+2))}{\\tan(5x+2)+\\sec(5x+2)}\\) does not simplify to \(5\\sec(5x+
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 2026-09-28 with SymPy 1.14.0.