Find d/dx sin(3x): animated lesson
A narrated, step-by-step derivatives video lesson with captions. Final answer: f'(x) = 3cos(3x).
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 (0.3 MB) · Captions (WebVTT)
Steps on screen
- 1. The problemFinding a derivative
- 2. Step by step
- Chain rule — d/dx[sin u] = cos u · u′
- Constant multiple rule
- Combine and simplify
- 3. The answer
f'(x) = 3cos(3x)
- 4. Check
- Cross-checked numerically against an independent symbolic differentiator at 8 sample points ✓
Transcript
The problem. Here is the problem: d by d x sin(3x). Find the derivative of sin(3 x) with respect to x.
Step by step. Chain rule — d by d x[sin u] equals cos u times u prime. Constant multiple rule. Combine and simplify.
The answer. So the answer is f prime of x equals 3cos(3x). 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.
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