Q.The area of the region bounded by the curve y=x+1 and the lines x=2 and x=3 is
(A) 27 sq units
(B) 29 sq units
(C) 211 sq units
(D) 213 sq units
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🔒 Start your 14-day free trial to unlock the full solution →Concept understanding — Area Under Curve
Area Under a Curve
How do you measure the area of a region whose top edge is curved rather than a straight line? For rectangles and triangles we have formulas, but a shape bounded above by y=f(x) has no simple side lengths to plug in. The definite integral is the tool built exactly for this.
The core idea: area as a limit of strips
Take the region under y=f(x) (with f(x)≥0), above the x-axis, between x=a and x=b. Slice it into many thin vertical strips. A strip at position x with tiny width dx is almost a rectangle of height f(x), so its area is about f(x)dx. Add up all the strips and let their width shrink to zero: the sum becomes the definite integral
Area=∫abf(x)dx.
This is why the integral is the area — it is the exact total of infinitely many infinitesimally thin rectangles.
How to compute it
Find an antiderivative F(x) (so F′(x)=f(x)) and evaluate at the two limits — the Fundamental Theorem of Calculus:
∫abf(x)dx=F(b)−F(a).
For example, the area under y=x2 from 0 to 1 is [3x3]01=31.
Cases you must handle carefully
The integral gives signed area. Where the curve dips below the x-axis, f(x)<0 and ∫fdx comes out negative. For the geometric (positive) area of such a stretch, integrate the absolute value or take the magnitude of that piece: Area=∫ab∣f(x)∣dx.
If a curve crosses the x-axis inside [a,b], split the integral at each crossing and add the sizes of the parts.
Area with respect to the y-axis
When the region is bounded by a curve x=g(y) and the y-axis between y=c and y=d, slice horizontally instead: …
The region is a trapezoid under the line y=x+1 from x=2 to x=3. The area is the definite integral of the curve between these limits.
Step 1: Write the area as
A=∫23(x+1)dx
Step 2: Integrate term by term:
∫(x+1)dx=2x2+x
Step 3: Evaluate from 2 to 3: …
The area under a curve between two vertical lines is the definite integral of the function over that interval. For y=x+1 from x=2 to x=3, the area is 27 square units, which corresponds to option (A).
The problem asks for the area bounded by a straight line and two vertical lines. This is a classic application of the Area Under the Curve (AUC) concept. When a curve y=f(x) lies above the x-axis over an interval [a,b], the area between the curve, the x-axis, and the lines x=a, x=b is given by the definite integral ∫abf(x)dx.
Here, y=x+1 is a straight line with slope 1 and intercept 1. Over x=2 to x=3, the function is positive (since x+1>0 for all x≥2). So the region is simply a trapezoid (or a rectangle plus a triangle) under the line. The integral will give us the exact area.
Let’s work through it step by step.
- Set up the integral. The area A is the definite integral of y=x+1 from x=2 to x=3:
A=∫23(x+1)dx
- Find the antiderivative. The antiderivative of x is 2x2, and the antiderivative of 1 is x. So:
∫(x+1)dx=2x2+x+C
- Evaluate the definite integral using the Fundamental Theorem of Calculus. Plug in the upper limit x=3 and the lower limit x=2, then subtract:
A=[2x2+x]23=(232+3)−(222+2)
- Simplify each term. At x=3: 29+3=29+26=215 At x=2: 24+2=2+2=4 So: …
Method: Area under a straight line between two vertical ordinates
Use this when the boundary is a line y=mx+c that stays above the x-axis between x=a and x=b.
Steps
Step 1: Check the line is positive across [a,b].
If y>0 throughout, the integral gives the area directly. (If it crosses the axis inside the interval, you would instead split at the crossing — not needed here.)
Step 2: Set up and evaluate the definite integral.
Area=∫ab(mx+c)dx=[2mx2+cx]ab …
Common Mistakes
Mistake 1: Subtracting the limits in the wrong order.
Why it's wrong: computing F(2)−F(3) instead of F(3)−F(2) flips the sign and gives −27. Correct approach: definite integrals are always upper minus lower, F(b)−F(a).
Mistake 2: Integrating x instead of the full x+1. …
Showing the 12 most recent of 20 on this concept.
- AP EAPCET 2026Set eng-2026-05-13-FN1 markMCQQ.The area of the region bounded by the curve y=x2+x, the lines y=x, x=1 and y=2 is (A) 512 (B) 27 (C) 54 (D) 31
›Reveal solutionSolution
The four boundary curves pin down a single closed loop from x=0 to x=1 between the parabola and the line y=x; its area is 31.
Concept and Intuition
When several curves are said to "bound a region," first locate every pairwise intersection — the closed loop's vertices are exactly these intersection points, and its area is found by integrating (upper curve minus lower curve) over the right interval.
Step-by-Step Solution
- Intersection of y=x2+x and y=x: x2+x=x⇒x2=0⇒x=0. They only touch at (0,0), and since x2+x−x=x2≥0, the parabola is above the line for all other x.
- Intersection of y=x and x=1: point (1,1).
- Intersection of y=x2+x and x=1: point (1,2).
- Intersection of y=x2+x and y=2: x2+x−2=0⇒(x−1)(x+2)=0⇒x=1 (the relevant root, giving (1,2) again). …
- AP EAPCET 2026Set eng-2026-05-14-AN1 markMCQQ.The area of the region enclosed between the curve y=loge(x+e) and the coordinate axes is (A) 4 (B) 3 (C) 2 (D) 1
›Reveal solutionSolution
The region bounded by y=log(x+e) and the two coordinate axes is a simple region between x=1−e (where the curve meets the x-axis) and x=0 (where it meets the y-axis); the area works out to exactly 1.
Concept and Intuition
To find the area enclosed between a curve and the coordinate axes, first locate where the curve crosses each axis — those crossing points bound the finite region. Here y=log(x+e) is a shifted, increasing logarithm; it crosses the y-axis at x=0 (giving y=loge=1) and the x-axis where log(x+e)=0, i.e. x+e=1, so x=1−e. Since the curve is positive throughout (1−e,0), the enclosed area is simply the definite integral of y over that interval.
Step-by-Step Solution
- Find the y-axis intercept: at x=0, y=log(0+e)=loge=1.
- Find the x-axis intercept: set log(x+e)=0⇒x+e=1⇒x=1−e (note 1−e≈−1.718).
- For x∈(1−e,0), the curve is increasing from 0 up to 1, staying non-negative, so the enclosed area is Area=∫1−e0log(x+e)dx. …
- AP EAPCET 2025Set eng-2025-05-23-FN1 markMCQQ.The area (in sq. units) of the region bounded by the lines x=0, x=2π and f(x)=sinx, g(x)=cosx is (A) 2(2−1) (B) 2(3−1) (C) 2(2+1) (D) 32+1
›Reveal solutionSolution
The two curves sinx and cosx cross at x=π/4 inside [0,π/2], so the enclosed area is the sum of two pieces, each evaluating to 2−1, giving total 2(2−1).
Concept and Intuition
Since sinx and cosx swap which one is larger at x=π/4, the area between them over [0,π/2] must be split at that crossing point and the absolute difference integrated on each side.
Step-by-Step Solution
- On [0,π/4]: cosx≥sinx, so area contribution is ∫0π/4(cosx−sinx)dx=[sinx+cosx]0π/4=(22+22)−(0+1)=2−1. …
- AP EAPCET 2024Set eng-2024-05-22-FN1 markMCQQ.The area (in sq. units) bounded by the curves x=y2 and x=3−2y2 is (A) 8 (B) 38 (C) 4 (D) 6
›Reveal solutionSolution
Integrate horizontally (with respect to y) since both curves are given as x= function of y. Answer: 4 square units.
Concept and Intuition
Both curves open sideways (they're expressed as x in terms of y), so it's natural to integrate along y, treating the region as bounded on the right by x=3−2y2 and on the left by x=y2, between their points of intersection.
Step-by-Step Solution
- Find intersection points: set y2=3−2y2⇒3y2=3⇒y2=1⇒y=±1.
- For −1≤y≤1, check which curve is to the right: at y=0, x=y2=0 vs x=3−2y2=3, so 3−2y2≥y2 throughout this range.
- Area =∫−11[(3−2y2)−y2]dy=∫−11(3−3y2)dy. …
- AP EAPCET 2023Set eng-2023-05-18-AN1 markMCQQ.The area bounded by y−1=−∣x∣ and y+1=∣x∣ is (A) 21 (B) 1 (C) 2 (D) 0
›Reveal solutionSolution
The two absolute-value "V" graphs cross at (±1,0) and enclose a rhombus-shaped region (a square rotated 45°) of area 2.
Concept and Intuition
y−1=−∣x∣⇒y=1−∣x∣ is an upside-down V peaking at (0,1) with slopes ∓1. y+1=∣x∣⇒y=∣x∣−1 is a right-side-up V bottoming at (0,−1) with slopes ±1. Since both have unit slopes, the enclosed figure is actually a square with diagonals along the axes (vertices at (0,1),(1,0),(0,−1),(−1,0)), i.e. a rhombus/square of diagonal length 2 each way.
Step-by-Step Solution
- Find intersections: 1−∣x∣=∣x∣−1⇒2=2∣x∣⇒∣x∣=1⇒x=±1, giving points (1,0) and (−1,0).
- On (−1,1), the top curve is y=1−∣x∣ (value 1 at x=0) and the bottom curve is y=∣x∣−1 (value −1 at x=0).
- Area =∫−11[(1−∣x∣)−(∣x∣−1)]dx=∫−11(2−2∣x∣)dx. …
- AP EAPCET 2026Set eng-2026-05-15-AN1 markMCQQ.The area enclosed between the curves y2=x and y=∣x∣ is (A) 61 (B) 31 (C) 21 (D) 32
›Reveal solutionSolution
Because y2=x only exists for x≥0, y=∣x∣ effectively reduces to the single ray y=x there; the enclosed area between the parabola and this line, from (0,0) to (1,1), is 61.
Concept and Intuition
y=∣x∣ is a V-shaped pair of rays, but the parabola y2=x only exists where x≥0 (since y2 can't be negative). So on the left half (x<0) there is no parabola to intersect the left ray of ∣x∣ — the only relevant intersection is between the parabola and the right ray y=x (x≥0). This reduces the problem to the classic area between y2=x and y=x.
Step-by-Step Solution
- Find intersection points: set y=x into y2=x: x2=x⇒x=0 or x=1. Points: (0,0) and (1,1).
- On [0,1], compare x (upper parabola branch) with x (the line): at x=0.25, x=0.5>0.25=x, so the parabola is above the line throughout (0,1). …
- AP EAPCET 2026Set eng-2026-05-12-FN1 markMCQQ.The area of the region bounded by the curve xy=−a (a>1) and the lines x=−a and y=a is (A) a(a−1−loga) (B) a(a+1+loga) (C) a2−a+loga (D) a2−a−loga
›Reveal solutionSolution
The area enclosed by the rectangular hyperbola xy=−a and the lines x=−a, y=a works out, after a direct integration, to a(a−1−loga).
Concept and Intuition
xy=−a (a>0) is a hyperbola lying in the second and fourth quadrants (since the product of coordinates must be negative). We only need the branch in the second quadrant here (x<0,y>0, i.e. y=−a/x). The two given lines pin down a finite region between the curve and the corner point where the lines would meet.
Step-by-Step Solution
- Rewrite the curve as y=−xa (valid for x<0 here, giving y>0).
- Find where the curve meets x=−a: y=−a/(−a)=1, point (−a,1).
- Find where the curve meets y=a: a=−a/x⇒x=−1, point (−1,a).
- For x∈[−a,−1], the curve y=−a/x lies below the line y=a (check at x=−1: curve value =a, equal; at x=−a: curve value=1<a since a>1). So the vertical strip between the curve and the top line y=a, from x=−a to x=−1, is exactly the bounded region.
- Area =∫−a−1[a−(−xa)]dx=∫−a−1(a+xa)dx. …
- AP EAPCET 2024Set eng-2024-05-21-FN1 markMCQQ.The area of the region under the curve y=∣sinx−cosx∣, 0≤x≤2π and above x-axis, is (in square units) (A) 22 (B) 22−1 (C) 2(2−1) (D) 2(2+1)
›Reveal solutionSolution
Split the region at x=π/4 where sinx=cosx, integrate each branch of the absolute value separately, and add.
Concept and Intuition
∣sinx−cosx∣ is cosx−sinx for x<π/4 (where cosine dominates) and sinx−cosx for x>π/4 (where sine dominates) — the area under an absolute-value curve must be computed piecewise across the sign change.
Step-by-Step Solution
- sinx=cosx at x=π/4 within [0,π/2]; for x<π/4, cosx>sinx, so ∣sinx−cosx∣=cosx−sinx; for x>π/4, it's sinx−cosx.
- ∫0π/4(cosx−sinx)dx=[sinx+cosx]0π/4=(22+22)−(0+1)=2−1. …
- AP EAPCET 2025Set eng-2025-05-22-FN1 markMCQQ.The area of the region lying between the curves y=4−x2, y2=3x and the Y-axis is (A) 3π−231 (B) 6π+231 (C) 3π+231 (D) 6π−231
›Reveal solutionSolution
Integrating with respect to y in two pieces — the parabola from y=0 to 3 and the circle from y=3 to 2 — gives the enclosed area as 3π−231.
Concept and Intuition
When a region's boundary is naturally expressed as x=x(y) for both curves (here x=4−y2 for the circle and x=y2/3 for the parabola), integrating along y with the y-axis as the common left boundary is far cleaner than integrating along x.
Step-by-Step Solution
- Find the intersection of y=4−x2 (so y2=4−x2) and y2=3x: 3x=4−x2⇒x2+3x−4=0⇒(x+4)(x−1)=0. Since x≥0 on the parabola, x=1, giving y=3.
- The circle meets the y-axis at (0,2); the parabola meets it at the origin (0,0).
- The enclosed region has: the y-axis as its left edge from (0,0) to (0,2); the parabola x=y2/3 as its right edge for y∈[0,3]; and the circle x=4−y2 as its right edge for y∈[3,2].
- Area =∫033y2dy+∫324−y2dy.
- First integral: ∫033y2dy=91[y3]03=933=33=31. …
- AP EAPCET 2025Set eng-2025-05-26-AN1 markMCQQ.The area of the region (in sq.units) bounded by the curves x2+y2=16 and y2=6x is (A) 4π+43 (B) 32(4π+3) (C) 34(4π+3) (D) 34π+3
›Reveal solutionSolution
The region common to the circle x2+y2=16 and parabola y2=6x is bounded by the parabola near the origin and the circle further out; integrating each piece and doubling for symmetry gives 34(4π+3).
Concept and Intuition
The parabola y2=6x opens rightward from the origin, and the circle has radius 4. Near the vertex, the parabola is the "narrower" curve (smaller ∣y∣ for given x), so it bounds the common region; farther out, the circle becomes narrower and takes over as the boundary. The crossover is exactly at their intersection point.
Step-by-Step Solution
- Intersection: substitute y2=6x into x2+y2=16: x2+6x−16=0⇒x=2 or x=−8 (rejected, since y2=6x≥0 needs x≥0). At x=2: y2=12⇒y=±23.
- For x∈[0,2]: parabola gives smaller ∣y∣ than the circle (check at x=1: parabola ∣y∣=6≈2.45, circle ∣y∣=15≈3.87) — so the parabola bounds the region here.
- For x∈[2,4]: circle gives smaller ∣y∣ (check at x=3: parabola ∣y∣=18≈4.24, circle ∣y∣=7≈2.65) — circle bounds here.
- Area (using symmetry about the x-axis, factor 2):
A=2[∫026xdx+∫2416−x2dx].
- ∫026xdx=6⋅32x3/202=6⋅32⋅22=383.
- Using ∫16−x2dx=2x16−x2+8sin−14x: …
- AP EAPCET 2023Set eng-2023-05-16-FN1 markMCQQ.The area bounded by the curves y−1=cosx, y=sinx and the X-axis between x=0 and x=π is (A) 2+2π (B) −2π (C) 2−2π (D) 2π
›Reveal solutionSolution
The area of the region bounded by y=1+cosx, y=sinx and the X-axis on [0,π] is 2π.
Concept and Intuition
Three curves fence off one closed region above the X-axis. Its floor is y=0; its roof is whichever curve is lower at each x (the lower envelope), because that is what actually caps the region touching the axis. So the area is the integral of min(1+cosx, sinx).
Step-by-Step Solution
- Find the crossing: 1+cosx=sinx⇒sinx−cosx=1⇒2sin(x−4π)=1, giving x=2π and x=π.
- On [0,2π]: at x=0, sinx=0<1+cosx=2, so sinx is the lower (roof) curve.
- On [2π,π]: at x=43π, 1+cosx≈0.29<sinx≈0.71, so 1+cosx is the roof.
- ∫0π/2sinxdx=[−cosx]0π/2=1.
- ∫π/2π(1+cosx)dx=[x+sinx]π/2π=π−(2π+1)=2π−1. …
- AP EAPCET 2023Set eng-2023-05-16-AN1 markMCQQ.The area bounded by the curve x=log(∣y∣), the lines x=−1 and x=0 is (A) 1−e−1 (B) 1−e (C) 2(1−e) (D) 2(1−e−1)
›Reveal solutionSolution
The curve x=log∣y∣ has two branches y=±ex; the area enclosed between x=−1 and x=0 is 2(1−e−1).
Concept and Intuition
x=log∣y∣⇔∣y∣=ex⇔y=±ex, giving a symmetric pair of curves about the x-axis.
Step-by-Step Solution
- Upper branch: y=ex. Lower branch: y=−ex.
- Between x=−1 and x=0, the vertical gap between the branches is ex−(−ex)=2ex. …
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