Q.Find the second order derivative of the function tan−1x.
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🔒 Start your 14-day free trial to unlock the full solution →Concept understanding — Successive Differentiation
Successive Differentiation — Repeated Slopes
Differentiate a function, then differentiate the result, then differentiate that, and so on. Each pass produces a new function describing a deeper layer of change. The physics picture makes it concrete: position → velocity (1st derivative) → acceleration (2nd) → jerk (3rd). Every step asks the same question: "how does the previous rate of change itself change?"
The definition and notation
If y=f(x), its successive derivatives are written y1,y2,…,yn, equivalently f′(x),f′′(x),…,f(n)(x) or dxdy,dx2d2y,…,dxndny. Each one is the derivative of the previous:
dxndny=dxd(dxn−1dn−1y).
| Order | Leibniz | Lagrange | Newton |
|---|---|---|---|
| 1st | dxdy | f′(x) | y˙ |
| 2nd | dx2d2y | f′′(x) | y¨ |
| nth | dxndny | f(n)(x) | — |
Seeing the pattern
Take y=x4: y1=4x3,y2=12x2,y3=24x,y4=24,y5=0. Each differentiation drops the degree by one, so a degree-n polynomial has a constant nth derivative and vanishing higher ones. Other families behave differently: eax never dies out (dxndneax=aneax), and sinx cycles every four steps (sin→cos→−sin→−cos).
Power rule applied n times: dxndn(xm)=m(m−1)⋯(m−n+1)xm−n for n≤m.
dx2d2y is not (dxdy)2 — a second derivative is not the square of the first derivative. …
Concept: Successive Differentiation — the second-order derivative is found by differentiating the first derivative again.
Step 1: y=tan−1x⇒y1=1+x21=(1+x2)−1. …
Differentiating y=tan−1x once gives y1=1+x21; differentiating again gives the second-order derivative y2=(1+x2)2−2x.
Step 1 — First derivative
Using the standard formula dxdtan−1x=1+x21:
y=tan−1x ⇒ y1=dxdy=1+x21=(1+x2)−1.
Step 2 — Differentiate again (second order)
Write y1=(1+x2)−1 and apply the chain rule together with the power rule:
y2=dxd[(1+x2)−1]=−1⋅(1+x2)−2⋅dxd(1+x2)=−(1+x2)−2⋅2x. …
Method: Finding a Second-Order Derivative of an Inverse Trig Function
The second derivative of tan−1x is found the same way as any other second-order derivative: differentiate once using the standard inverse-trig derivative, then differentiate that result again using the chain rule on a negative power.
Steps
Step 1: Find the first derivative
y=tan−1x⇒y1=1+x21=(1+x2)−1.
Step 2: Differentiate y1 again using the chain rule
Treat (1+x2)−1 as a composite function: the outer function is u−1 (derivative −u−2) and the inner function is u=1+x2 (derivative 2x).
y2=−(1+x2)−2⋅2x=−(1+x2)22x. …
Common Mistakes
Mistake 1: Forgetting the chain rule when differentiating (1+x2)−1 a second time.
Why it's wrong: writing y2=−(1+x2)−2 without the extra factor 2x (the derivative of the inner 1+x2) misses half the required chain-rule expansion. Correct approach: always differentiate the inner function 1+x2 explicitly and multiply it in.
Mistake 2: Confusing "second derivative" with "principal value branch". …
Showing the 12 most recent of 22 on this concept.
- CBSE 2026Set A1 markMCQQ.dx2d2(sin2x)=(a) 4sin2x(b) 4cos22x(c) −4sin2x(d) 2sin4x
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dx2d2(sin2x)=−4sin2x.
First derivative (chain rule):
dxd(sin2x)=2cos2x.
Second derivative: …
- CBSE 2026Set ANNUAL1 markQ.If y = 8e⁻³ˣ, find d²y/dx².
›Reveal solutionSolution
Differentiate y=8e−3x twice using the chain rule.
dxdy=8⋅(−3)e−3x=−24e−3x
…
- CBSE 2026Set ANNUAL1 markQ.Find the second derivative for the function y=sin x + e^{2x}.
›Reveal solutionSolution
y′′=−sinx+4e2x.
Concept. The second derivative is found by differentiating the first derivative; use dxdsinx=cosx and dxdekx=kekx.
Steps.
- y=sinx+e2x.
- First derivative: y′=cosx+2e2x. …
- CBSE 2025Set ANNUAL1 markQ.Find the second order derivative of the function y=logx.
›Reveal solutionSolution
Differentiate y=logx twice.
y=logx⟹dxdy=x1
…
- CBSE 2025Set ANNUAL1 markMCQQ.If y=2sinx+3cosx then dx2d2y=(a) y(b) y1(c) −y(d) −y1
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Differentiate twice — the second derivative comes back around to -y, a classic SHM-type result.
y=2sinx+3cosx
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…
- CBSE 2025Set ANNUAL1 markQ.Find the second-order derivative of xcosx w.r.t. x.
›Reveal solutionSolution
Apply the product rule twice.
Let y=xcosx.
First derivative (product rule on x and cosx):
y′=dxd(x)cosx+xdxd(cosx)=1⋅cosx+x(−sinx)=cosx−xsinx.
Second derivative (differentiate cosx and the product xsinx): …
- CBSE 2024Set D1 markMCQQ.If y=x20 then dx2d2y=(a) x18(b) 20x19(c) 380x18(d) x19
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dx2d2y=380x18.
Use the power rule dxdxn=nxn−1 twice.
First derivative:
dxdy=20x19.
Second derivative: …
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Differentiate y=log x twice: first derivative is 1/x, second derivative is -1/x^2.
y=logx⇒dxdy=x1=x−1
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- CBSE 2024Set ANNUAL1 markQ.Find the second-order derivative of logx.
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Differentiate logx twice.
Let y=logx. The first derivative is
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Differentiating again, …
- CBSE 2023Set E1 markMCQQ.dx2d2(e5x)=(a) e5x(b) 10e5x(c) 5e5x(d) 25e5x
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dxde5x=5e5x, and differentiating again gives 25e5x.
First derivative: dxde5x=5e5x.
…
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Differentiate y=xlogex twice using the product rule.
Given y=xlogex.
First derivative (product rule, u=x, v=logex):
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…
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Differentiate twice by the chain rule; each derivative brings down a factor of 3, and differentiating sine twice turns it into −sin.
Let y=sin(3x+5).
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…
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