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DerivativesCalculusCollegeabout 1:35

Derivative of (ln(3x-2))/(cos(e^(x)+1)): animated lesson

A narrated, step-by-step derivatives video lesson with captions. Final answer: f'(x) = (3 / (3 x - 2) + ln(3 x - 2)·sin(e^x + 1)·e^x / cos(e^x + 1)) / cos(e^x + 1).

Video with a synthetic English voice and captions. Pick another language for subtitles in that language, or open the interactive version.

Video narrated by a synthetic voice (Piper TTS, en_US-ljspeech-high voice (LJ Speech dataset, public domain)); the steps come from our maths engine and the answer was checked independently. Download MP4 (0.7 MB) · Captions (WebVTT)

Steps on screen

  1. 1. The problem
    Finding a derivative
    ddx[ln⁡(3x−2)cos⁡(ex+1)]\frac{d}{dx}\left[\frac{\ln\left(3x-2\right)}{\cos\left({e}^{x}+1\right)}\right]
  2. 2. Steps, part 1
    1. ddx[ln⁡(3x−2)cos⁡(ex+1)]=33x−2+ln⁡(3x−2)sin⁡(ex+1)excos⁡(ex+1)cos⁡(ex+1)\frac{d}{dx}\left[\frac{\ln\left(3x-2\right)}{\cos\left({e}^{x}+1\right)}\right] = \frac{\frac{3}{3x-2}+\frac{\ln\left(3x-2\right) \sin\left({e}^{x}+1\right) {e}^{x}}{\cos\left({e}^{x}+1\right)}}{\cos\left({e}^{x}+1\right)}
      Quotient rule: (u/v)′ = (u′v − uv′)/v²
    2. ddx[cos⁡(ex+1)]=−(sin⁡(ex+1)ex)\frac{d}{dx}\left[\cos\left({e}^{x}+1\right)\right] = -\left(\sin\left({e}^{x}+1\right) {e}^{x}\right)
      Chain rule — d/dx[cos u] = −sin u · u′
    3. ddx[ex+1]=ex\frac{d}{dx}\left[{e}^{x}+1\right] = {e}^{x}
      Sum rule: differentiate each term separately
    4. ddx[ex]=ex\frac{d}{dx}\left[{e}^{x}\right] = {e}^{x}
      Exponential rule: d/dx[eᵘ] = eᵘ·u′
  3. 3. Steps, part 2
    1. ddx[ln⁡(3x−2)]=33x−2\frac{d}{dx}\left[\ln\left(3x-2\right)\right] = \frac{3}{3x-2}
      Chain rule — d/dx[ln u] = u′/u
    2. ddx[3x−2]=3\frac{d}{dx}\left[3x-2\right] = 3
      Difference rule: differentiate each term separately
    3. ddx[3x]=3\frac{d}{dx}\left[3x\right] = 3
      Constant multiple rule
    4. f′(x)=33x−2+ln⁡(3x−2)sin⁡(ex+1)excos⁡(ex+1)cos⁡(ex+1)f'(x) = \frac{\frac{3}{3x-2}+\frac{\ln\left(3x-2\right) \sin\left({e}^{x}+1\right) {e}^{x}}{\cos\left({e}^{x}+1\right)}}{\cos\left({e}^{x}+1\right)}
      Combine and simplify
  4. 4. The answer
    f′(x)=33x−2+ln⁡(3x−2)sin⁡(ex+1)excos⁡(ex+1)cos⁡(ex+1)f'(x) = \frac{\frac{3}{3x-2}+\frac{\ln\left(3x-2\right) \sin\left({e}^{x}+1\right) {e}^{x}}{\cos\left({e}^{x}+1\right)}}{\cos\left({e}^{x}+1\right)}

    f'(x) = (3 / (3 x - 2) + ln(3 x - 2)·sin(e^x + 1)·e^x / cos(e^x + 1)) / cos(e^x + 1)

  5. 5. Check
    • Cross-checked numerically against an independent symbolic differentiator at 8 sample points ✓

Transcript

The problem. Here is the problem: derivative of (ln(3x minus 2))/(cos(e to the power x plus 1)). Find the derivative of (ln(3 x minus 2)) / (cos(e to the power x plus 1)) with respect to x.

Steps, part 1. Quotient rule: (u/v) prime equals (u prime v minus uv prime )/v squared. Chain rule — d by d x[cos u] equals negative sin u times u prime. Sum rule: differentiate each term separately. Exponential rule: d by d x[eᵘ] equals eᵘ times u prime.

Steps, part 2. Chain rule — d by d x[ln u] equals u prime /u. Difference rule: differentiate each term separately. Constant multiple rule. Combine and simplify.

The answer. So the answer is f prime of x equals (3 / (3 x minus 2) plus ln(3 x minus 2) times sin(e to the power x plus 1) times e to the power x / cos(e to the power x plus 1)) / cos(e to the power x plus 1). The derivative is built from the outside in: sums split into terms, constants factor out, products and quotients use their rules, and every composite function multiplies by the derivative of its inside (chain rule).

Check. Cross-checked numerically against an independent symbolic differentiator at 8 sample points, which checks out.

About derivatives

Differentiate with the power, product, quotient and chain rules, including higher derivatives.

Derivative of (ln(3x-2))/(cos(e^(x)+1)): Derivatives Lesson