Q.Evaluate: ∫cos2(exx)ex(1+x)dx.
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Antiderivatives by Inspection
The idea
Many integrals do not need a formal method at all. If you already know the derivative of some standard function, you can often recognise the answer just by looking — you spot which function differentiates to give the integrand, then adjust a constant if needed. This is finding an antiderivative by inspection: read the integrand backwards through your table of derivatives.
Integration is the reverse of differentiation, so a strong memory of standard derivatives is really a table of standard integrals read the other way.
Straight recognition
Because dxd(sinx)=cosx, you immediately write ∫cosxdx=sinx+C. No working — you inspect and recognise. The same holds for the standard list: ∫sec2xdx=tanx+C, ∫exdx=ex+C, ∫x1dx=log∣x∣+C, and so on.
Guess-and-adjust
Often the integrand is close to a known derivative but off by a constant factor. You guess the likely antiderivative, differentiate it mentally, and rescale so it matches.
Example: find ∫cos2xdx. Guess sin2x. Differentiating gives 2cos2x — twice too big — so divide the guess by 2:
∫cos2xdx=21sin2x+C.
Example: ∫(2x+1)5dx. Guess (2x+1)6; its derivative is 6(2x+1)5⋅2=12(2x+1)5, so divide by 12:
∫(2x+1)5dx=121(2x+1)6+C.
The one safeguard …
Notice eˣ(1+x) = d/dx(x eˣ); substitute t = x eˣ. …
With t = x eˣ (so dt = eˣ(1+x)dx), the integral becomes ∫sec²t dt = tan(x eˣ) + C.
We evaluate ∫ eˣ(1 + x) / cos²(x eˣ) dx.
Step 1: Let t = x eˣ. Then dt/dx = eˣ + x eˣ = eˣ(1 + x), so dt = eˣ(1 + x) dx.
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Showing the 12 most recent of 27 on this concept.
- CBSE 2026Set V11 markMCQQ.The antiderivative of xx2−11, x>1 with respect to x(a) sin−1x+c(b) cos−1x+c(c) −cosec−1x+c(d) cot−1x+c
›Reveal solutionSolution
The standard antiderivative is sec−1x, which equals −cosec−1x+c; answer (c).
The standard result is
∫xx2−1dx=sec−1∣x∣+c,x>1.
Since sec−1x+cosec−1x=2π (a constant), we have sec−1x=2π−cosec−1x, so the antiderivative can equally be written …
- CBSE 2025Set A1 markQ.Match the correct pair. Column A (i): ∫x2+a2dx. Column B options:(a) log∣sinx∣+c(b) 2xx2−9−29logx+x2−9+c(c) csc−1x(d) logx+x2−9+c(e) 2xx2+a2+2a2logx+x2+a2+c(f) logx+x2+a2+c(g) log∣secx∣+c. Write the letter of the option that matches Column A (i).
›Reveal solutionSolution
This is the standard NCERT integral formula ∫x2+a2dx=logx+x2+a2+c.
This is one of the standard results proved (in the NCERT text) using the substitution x=atanθ: …
- CBSE 2025Set A1 markQ.Match the correct pair. Column A (ii): ∫x2+a2dx. Column B options:(a) log∣sinx∣+c(b) 2xx2−9−29logx+x2−9+c(c) csc−1x(d) logx+x2−9+c(e) 2xx2+a2+2a2logx+x2+a2+c(f) logx+x2+a2+c(g) log∣secx∣+c. Write the letter of the option that matches Column A (ii).
›Reveal solutionSolution
This is the standard NCERT formula for ∫x2+a2dx.
This is a standard result (derived in the NCERT text via integration by parts): …
- CBSE 2025Set A1 markQ.Match the correct pair. Column A (iii): ∫tanxdx. Column B options:(a) log∣sinx∣+c(b) 2xx2−9−29logx+x2−9+c(c) csc−1x(d) logx+x2−9+c(e) 2xx2+a2+2a2logx+x2+a2+c(f) logx+x2+a2+c(g) log∣secx∣+c. Write the letter of the option that matches Column A (iii).
›Reveal solutionSolution
Write tanx=sinx/cosx and integrate by substitution u=cosx.
∫tanxdx=∫cosxsinxdx
Let u=cosx, du=−sinxdx: …
- CBSE 2025Set A1 markQ.Match the correct pair. Column A (iv): ∫cotxdx. Column B options:(a) log∣sinx∣+c(b) 2xx2−9−29logx+x2−9+c(c) csc−1x(d) logx+x2−9+c(e) 2xx2+a2+2a2logx+x2+a2+c(f) logx+x2+a2+c(g) log∣secx∣+c. Write the letter of the option that matches Column A (iv).
›Reveal solutionSolution
Write cotx=cosx/sinx and integrate by substitution u=sinx.
∫cotxdx=∫sinxcosxdx
Let u=sinx, du=cosxdx: …
- CBSE 2025Set A1 markQ.Match the correct pair. Column A (v): ∫x2−9dx. Column B options:(a) log∣sinx∣+c(b) 2xx2−9−29logx+x2−9+c(c) csc−1x(d) logx+x2−9+c(e) 2xx2+a2+2a2logx+x2+a2+c(f) logx+x2+a2+c(g) log∣secx∣+c. Write the letter of the option that matches Column A (v).
›Reveal solutionSolution
This is the standard NCERT formula ∫x2−a2dx with a=3.
The standard result (by parts, same family as ∫x2+a2dx but with a sign change) is:
∫x2−a2dx=2xx2−a2−2a2logx+x2−a2+c
With a2=9 (i.e. a=3): …
- CBSE 2025Set A1 markQ.Match the correct pair. Column A (vi): ∫x2−9dx. Column B options:(a) log∣sinx∣+c(b) 2xx2−9−29logx+x2−9+c(c) csc−1x(d) logx+x2−9+c(e) 2xx2+a2+2a2logx+x2+a2+c(f) logx+x2+a2+c(g) log∣secx∣+c. Write the letter of the option that matches Column A (vi).
›Reveal solutionSolution
This is the standard NCERT formula ∫x2−a2dx with a=3.
The standard result (by substitution x=asecθ) is:
∫x2−a2dx=logx+x2−a2+c
With a=3: …
- CBSE 2025Set ANNUAL1 markQ.Find an anti-derivative of (ax+b)2 by the method of inspection. OR Find the order and degree of the differential equation dx2d2y+5x(dxdy)2−6y=logx
›Reveal solutionSolution
Guess a cube and adjust the constant so its derivative reproduces (ax+b)2.
We seek F(x) with F′(x)=(ax+b)2. Trying F(x)=(ax+b)3:
dxd(ax+b)3=3(ax+b)2⋅a=3a(ax+b)2,
which is 3a times too large. Dividing by 3a:
dxd[3a(ax+b)3]=(ax+b)2.
…
- CBSE 2024Set ANNUAL1 markMCQQ.∫011−x21dx=(a) 2π(b) 4π(c) 32π(d) 23π
›Reveal solutionSolution
Integrate 1/√(1-x^2) to get sin^{-1}x, then evaluate between 0 and 1.
…
- CBSE 2024Set ANNUAL1 markQ.Evaluate : ∫9−25x2dx OR Integrate w.r.t. x : x+xlogx1
›Reveal solutionSolution
Reduce to the standard form ∫a2−x2dx=sin−1ax.
Rewrite the denominator:
9−25x2=25(259−x2)=5(53)2−x2.
So
∫9−25x2dx=51∫(3/5)2−x2dx=51sin−13/5x+C=51sin−135x+C.
…
- CBSE 2023Set 65/1/11 markMCQQ.∫0π/6sec2(x−6π)dx is equal to:(a) 31(b) −31(c) 3(d) −3
›Reveal solutionSolution
The integral simplifies by noticing the derivative of tan is sec2, so the antiderivative is tan(x−6π). Evaluating from 0 to 6π gives 31, which is option (a).
The key here is recognising that sec2 is the derivative of tan. That means the integral is essentially a direct application of the fundamental theorem — no substitution or trickery needed. The only subtlety is handling the shift inside the argument: x−6π just shifts the tangent function horizontally, which doesn't change the fact that its derivative is sec2 of the same argument.
- Identify the antiderivative. We know dxdtanu=sec2u⋅dxdu. Here u=x−6π, so dxdu=1. Therefore,
∫sec2(x−6π)dx=tan(x−6π)+C.
- Apply the limits. The definite integral from 0 to 6π is:
[tan(x−6π)]0π/6=tan(6π−6π)−tan(0−6π).
- Simplify each term.
- At the upper limit: tan(0)=0.
- At the lower limit: tan(−6π). Since tan is an odd function, tan(−θ)=−tanθ, so
tan(−6π)=−tan(6π)=−31.
- Compute the difference. …
- CBSE 2023Set E1 markMCQQ.∫sin43xdx=(a) k−43cos43x(b) k+43cos43x(c) k−34cos43x(d) k+34cos43x
›Reveal solutionSolution
∫sin43xdx=−34cos43x+k.
Using ∫sin(ax)dx=−a1cos(ax) with a=43:
…
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