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DerivativesCalculusCollegeabout 1:17

Derivative of (sqrt(3x-2))(cos(3x-2)): animated lesson

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

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 (0.5 MB) · Captions (WebVTT)

Steps on screen

  1. 1. The problem
    Finding a derivative
    ddx[3x−2cos⁡(3x−2)]\frac{d}{dx}\left[\sqrt{3x-2} \cos\left(3x-2\right)\right]
  2. 2. Steps, part 1
    1. ddx[3x−2cos⁡(3x−2)]=cos⁡(3x−2)⋅32−33x−22sin⁡(3x−2)3x−2\frac{d}{dx}\left[\sqrt{3x-2} \cos\left(3x-2\right)\right] = \frac{\frac{\cos\left(3x-2\right)\cdot3}{2}-3 {\sqrt{3x-2}}^{2} \sin\left(3x-2\right)}{\sqrt{3x-2}}
      Product rule: (uv)′ = u′v + uv′
    2. ddx[cos⁡(3x−2)]=−(3sin⁡(3x−2))\frac{d}{dx}\left[\cos\left(3x-2\right)\right] = -\left(3\sin\left(3x-2\right)\right)
      Chain rule — d/dx[cos u] = −sin u · u′
    3. ddx[3x−2]=323x−2\frac{d}{dx}\left[\sqrt{3x-2}\right] = \frac{\frac{3}{2}}{\sqrt{3x-2}}
      Chain rule — d/dx[√u] = u′/(2√u)
    4. ddx[3x−2]=3\frac{d}{dx}\left[3x-2\right] = 3
      Difference rule: differentiate each term separately
  3. 3. Steps, part 2
    1. ddx[3x]=3\frac{d}{dx}\left[3x\right] = 3
      Constant multiple rule
    2. f′(x)=cos⁡(3x−2)⋅32−33x−22sin⁡(3x−2)3x−2f'(x) = \frac{\frac{\cos\left(3x-2\right)\cdot3}{2}-3 {\sqrt{3x-2}}^{2} \sin\left(3x-2\right)}{\sqrt{3x-2}}
      Combine and simplify
  4. 4. The answer
    f′(x)=cos⁡(3x−2)⋅32−33x−22sin⁡(3x−2)3x−2f'(x) = \frac{\frac{\cos\left(3x-2\right)\cdot3}{2}-3 {\sqrt{3x-2}}^{2} \sin\left(3x-2\right)}{\sqrt{3x-2}}

    f'(x) = (cos(3 x - 2)·3/2 - 3sqrt(3 x - 2)²·sin(3 x - 2)) / sqrt(3 x - 2)

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

Transcript

The problem. Here is the problem: derivative of (sqrt(3x minus 2))(cos(3x minus 2)). Find the derivative of (sqrt(3 x minus 2)) (cos(3 x minus 2)) with respect to x.

Steps, part 1. Product rule: (uv) prime equals u prime v plus uv prime. Chain rule — d by d x[cos u] equals negative sin u times u prime. Chain rule — d by d x[the square root of u] equals u prime /(2the square root of u. Difference rule: differentiate each term separately.

Steps, part 2. Constant multiple rule. Combine and simplify.

The answer. So the answer is f prime of x equals (cos(3 x minus 2) times 3 over 2 minus 3sqrt(3 x minus 2) squared times sin(3 x minus 2)) / sqrt(3 x minus 2). 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 (sqrt(3x-2))(cos(3x-2)): Derivatives Lesson