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Derivative of (sin(x^2+1))/(arctan(x^2+1)): animated lesson

A narrated, step-by-step derivatives video lesson with captions. Final answer: f'(x) = (2cos(x² + 1) / atan(x² + 1) - 2(1 / atan(x² + 1))²·sin(x² + 1) / ((x² + 1)² + 1))·x.

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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 (0.6 MB) · Captions (WebVTT)

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1. The problem
Finding a derivative
$\frac{d}{dx}\left[\frac{\sin\left({x}^{2}+1\right)}{\tan^{-1}\left({x}^{2}+1\right)}\right]$
2. Steps, part 1
1. $\frac{d}{dx}\left[\frac{\sin\left({x}^{2}+1\right)}{\tan^{-1}\left({x}^{2}+1\right)}\right] = \left(\frac{2\cos\left({x}^{2}+1\right)}{\tan^{-1}\left({x}^{2}+1\right)}-\frac{2 \left({\frac{1}{\tan^{-1}\left({x}^{2}+1\right)}}\right)^{2} \sin\left({x}^{2}+1\right)}{{\left({x}^{2}+1\right)}^{2}+1}\right) x$
  Quotient rule: (u/v)′ = (u′v − uv′)/v²
2. $\frac{d}{dx}\left[\tan^{-1}\left({x}^{2}+1\right)\right] = \frac{2x}{{\left({x}^{2}+1\right)}^{2}+1}$
  Chain rule — d/dx[arctan u] = u′/(1 + u²)
3. $\frac{d}{dx}\left[\sin\left({x}^{2}+1\right)\right] = 2\cos\left({x}^{2}+1\right) x$
  Chain rule — d/dx[sin u] = cos u · u′
4. $\frac{d}{dx}\left[{x}^{2}+1\right] = 2x$
  Sum rule: differentiate each term separately
3. Steps, part 2
1. $\frac{d}{dx}\left[{x}^{2}\right] = 2x$
  Power rule: d/dx[xⁿ] = n·xⁿ⁻¹
2. $f'(x) = \left(\frac{2\cos\left({x}^{2}+1\right)}{\tan^{-1}\left({x}^{2}+1\right)}-\frac{2 \left({\frac{1}{\tan^{-1}\left({x}^{2}+1\right)}}\right)^{2} \sin\left({x}^{2}+1\right)}{{\left({x}^{2}+1\right)}^{2}+1}\right) x$
  Combine and simplify
4. The answer
$f'(x) = \left(\frac{2\cos\left({x}^{2}+1\right)}{\tan^{-1}\left({x}^{2}+1\right)}-\frac{2 \left({\frac{1}{\tan^{-1}\left({x}^{2}+1\right)}}\right)^{2} \sin\left({x}^{2}+1\right)}{{\left({x}^{2}+1\right)}^{2}+1}\right) x$
f'(x) = (2cos(x² + 1) / atan(x² + 1) - 2(1 / atan(x² + 1))²·sin(x² + 1) / ((x² + 1)² + 1))·x
5. Check
- Cross-checked numerically against an independent symbolic differentiator at 8 sample points ✓

Transcript

The problem. Here is the problem: derivative of (sin(x squared plus 1))/(arctan(x squared plus 1)). Find the derivative of (sin(x squared plus 1)) / (atan(x squared 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[arctan u] equals u prime /(1 plus u squared). Chain rule — d by d x[sin u] equals cos u times u prime. Sum rule: differentiate each term separately.

Steps, part 2. Power rule: d by d x[x to the power n] equals n times x to the power n minus 1. Combine and simplify.

The answer. So the answer is f prime of x equals (2cos(x squared plus 1) / atan(x squared plus 1) minus 2(1 / atan(x squared plus 1)) squared times sin(x squared plus 1) / ((x squared plus 1) squared plus 1)) times x. 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 (sin(x^2+1))/(arctan(x^2+1)): Animated Lesson