Q.A student observes an open-air Honeybee nest on the branch of a tree, whose plane figure is parabolic shape given by x2=4y. Then the area (in sq units) of the region bounded by parabola x2=4y and the line y=4 is
(A) 332
(B) 364
(C) 3128
(D) 3256
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🔒 Start your 14-day free trial to unlock the full solution →Concept understanding — Area Under Parabola
Area Under a Parabola
Picture the simplest parabola, y=x2: a smooth U opening upward with its lowest point at the origin. Suppose we want the area trapped between this curve, the x-axis, and the vertical lines x=0 and x=1 — the area under the parabola on [0,1].
A rough estimate helps. A rectangle of base 1 and height 1 gives area 1 — too big, since the curve sits well below its top. A triangle gives 21×1×1=0.5 — too small, since the curve bulges above the straight edge. So the true area lies somewhere between 0.5 and 1.
Calculus pins it down exactly. The area under a curve y=f(x) from x=a to x=b (with f(x)≥0) is the definite integral
Area=∫abf(x)dx.
For y=x2 from 0 to 1 we use the power rule
∫xndx=n+1xn+1+C(n=−1)
so, with n=2,
∫01x2dx=[3x3]01=31−0=31.
The exact area is 31 square units (about 0.333) — comfortably between our two guesses.
The area is exactly one-third of the bounding rectangle. In general, under y=x2 from 0 to a the area is 3a3, i.e. one-third of the a×a2 rectangle.
The general statement
For y=kx2 (k constant), the area from x=a to x=b is
∫abkx2dx=k⋅3b3−a3.
If the parabola is shifted, such as y=x2+c, integrate term by term. If it opens sideways, such as x=y2, integrate with respect to y instead. …
Concept: Area Under Parabola – The region is bounded by the parabola x2=4y and the horizontal line y=4.
Step 1: The parabola opens upward with vertex at the origin. The line y=4 cuts the parabola where x2=16, so x=±4.
Step 2: The required area is symmetric about the y-axis. Using vertical strips, area from x=−4 to x=4 between the line and the parabola:
Area=∫−44(4−4x2)dx
Step 3: By symmetry, compute twice the area from 0 to 4: …
The area between the parabola x2=4y and the horizontal line y=4 is found by integrating the horizontal width of the region with respect to y. The result is 364 square units, which corresponds to option (B).
The key insight here is that the parabola x2=4y opens upward, with its vertex at the origin. The line y=4 is a horizontal line cutting across it. The region bounded between them is symmetric about the y-axis, so we can find the area in the right half and double it.
When a region is bounded by a curve and a horizontal line, it's often easier to integrate with respect to y rather than x. Why? Because the boundaries become simple: the left and right boundaries are given by the parabola, and the top and bottom boundaries are horizontal lines. Integrating along y means we slice the region into thin horizontal strips, each of which has a simple rectangular shape.
Let's work through it step by step.
-
Find the intersection points.
The parabola is x2=4y and the line is y=4. Substituting y=4 into the parabola gives x2=16, so x=±4. The region runs from x=−4 to x=4 horizontally, and from y=0 (the vertex) to y=4 vertically.
-
Set up the integral with respect to y.
For a fixed y, the parabola gives x=±2y. The horizontal width of the region at that y is the distance between the right and left branches:
width=2y−(−2y)=4y.
The area is the sum (integral) of these widths over y from 0 to 4:
Area=∫y=044ydy.
- Evaluate the integral.
∫4ydy=4⋅32y3/2=38y3/2.
Applying the limits:
[38y3/2]04=38(43/2−0)=38⋅8=364. …
Method: Area between a curve and a horizontal line
Use this whenever a region is enclosed by a parabola (or similar curve) and a horizontal line y=k. Choosing the right slicing direction turns a messy integral into a clean one.
Steps
Step 1: Find the intersection points.
Set the line's value into the curve. For x2=4y and y=k, that gives x=±2k — these fix the horizontal extent of the region.
Step 2: Decide the slicing direction.
For a region capped by a horizontal line, integrating with respect to y is usually cleanest: horizontal strips have width = (right branch) − (left branch).
width(y)=24-type expression from x=±4y.
Step 3: Set up the definite integral of the strip width. …
Common Mistakes
Mistake 1: Integrating the parabola alone and forgetting to subtract.
Why it's wrong: ∫4x2dx gives the area under the parabola, not the region between it and y=4. Correct approach: the bounded area is (rectangle 8×4=32) − (area under parabola =332) =364, or integrate the strip width directly.
Mistake 2: Wrong strip width from the parabola. …
Showing the 12 most recent of 22 on this concept.
- TG EAPCET 2021Set eng-2021-08-06-FN1 markMCQQ.The area of a triangle (in sq. units) formed by the latus rectum of the parabola x2=16y and the lines joining the vertex of the parabola to the ends of the latus rectum is (A) 24 (B) 28 (C) 32 (D) 64
›Reveal solutionSolution
The problem asks for the area of a triangle formed by the vertex of the parabola x2=16y and the endpoints of its latus rectum. By identifying the parabola's properties, finding the coordinates of the vertex and the latus rectum's endpoints, and then using the formula for the area of a triangle, we find the area to be 32 square units.
The core idea here is to first understand the geometry of a parabola and its key features: the vertex and the latus rectum. Once these geometric elements are identified and their coordinates determined, calculating the area of the triangle becomes a straightforward application of the area formula.
The given parabola is x2=16y. This equation is in the standard form x2=4ay, which describes a parabola opening upwards with its vertex at the origin (0,0).
The latus rectum of a parabola is a line segment that passes through the focus, is perpendicular to the axis of symmetry, and has its endpoints on the parabola. For a parabola of the form x2=4ay, the focus is at (0,a), and the latus rectum is the horizontal line segment y=a with length 4a.
The triangle in question has three vertices:
- The vertex of the parabola.
- One end of the latus rectum.
- The other end of the latus rectum.
We can find the coordinates of these three points and then use the standard formula for the area of a triangle given its vertices. Alternatively, recognizing that the base of this triangle (the latus rectum) is horizontal and the vertex of the parabola is on the y-axis, we can use the simple formula 21×base×height.
-
Identify the properties of the parabola:
The given equation of the parabola is x2=16y.
Comparing this with the standard form x2=4ay, we can determine the value of a.
4a=16
a=416
a=4
For a parabola of the form x2=4ay:
- The vertex is at the origin, V=(0,0).
- The focus is at (0,a), which is F=(0,4).
- The axis of the parabola is the y-axis.
-
Determine the endpoints of the latus rectum:
The latus rectum is a line segment passing through the focus (0,4) and perpendicular to the axis of the parabola (the y-axis). Therefore, the equation of the line containing the latus rectum is y=4.
To find the endpoints of the latus rectum, substitute y=4 into the parabola's equation:
x2=16(4)
x2=64
Taking the square root of both sides:
x=±64
x=±8
So, the endpoints of the latus rectum are L1=(−8,4) and L2=(8,4).
TipThe length of the latus rectum for x2=4ay is 4a. In this case, 4a=16. The endpoints are (±2a,a). Here, 2a=2(4)=8, so the endpoints are (±8,4), which matches our calculation.
-
Identify the vertices of the triangle:
The triangle is formed by the vertex of the parabola and the ends of the latus rectum.
The vertices are:
- V=(0,0)
- L1=(−8,4)
- L2=(8,4)
-
Calculate the area of the triangle: …
- TG EAPCET 2025Set eng-2025-05-04-AN1 markMCQQ.The area of the region bounded by y=x3, x-axis, x=−2 and x=4 is (A) 64 (B) 481 (C) 566 (D) 68
›Reveal solutionSolution
The area is the sum of the absolute values of the definite integrals from x=−2 to x=0 and from x=0 to x=4, because the curve lies below the x-axis on the left interval and above it on the right. The total area is 68, so the correct option is (D).
The key concept here is that area between a curve and the x-axis is always taken as a positive quantity. When a function dips below the x-axis, the definite integral gives a negative number, but area is the absolute value of that signed area. So we must split the region at the x-intercept(s) where the curve crosses the axis, integrate each piece separately, take the absolute value, and then add them.
For y=x3, the only x-intercept is at x=0. Between x=−2 and x=0, the curve is below the axis (since x3 is negative for negative x). Between x=0 and x=4, the curve is above the axis. Therefore, the total area is:
Area=∫−20x3dx+∫04x3dx
Now we compute step by step.
-
Integrate x3
The antiderivative is 4x4.
-
Evaluate from x=−2 to x=0
∫−20x3dx=[4x4]−20=404−4(−2)4=0−416=−4
The signed area is −4, so the actual (positive) area is ∣−4∣=4.
- Evaluate from x=0 to x=4 ∫04x3dx=[4x4]04=444−404=4256−0=64…
-
- TG EAPCET 2024Set eng-2024-05-10-FN1 markMCQQ.The area of the region enclosed by the curves y2=4(x+1) and y2=5(x−4) is (A) 3280 (B) 150 (C) 140 (D) 3200
›Reveal solutionSolution
The parabolas meet at y=±10; integrating the horizontal width 5−20y2 gives area 3200.
Set up horizontal strips. Solving each curve for x:
x1=4y2−1(from y2=4(x+1)),x2=5y2+4(from y2=5(x−4)).
Intersection points. Setting x1=x2:
4y2−5y2=5⟹20y2=5⟹y2=100⟹y=±10,
with common x=24.
Width of a strip. For ∣y∣<10 the curve x2 lies to the right of x1:
x2−x1=(5y2+4)−(4y2−1)=5−20y2. …
- TG EAPCET 2026Set eng-2026-05-11-AN1 markMCQQ.The area of the region bounded by the curves y=x2+1, x=y2+1, X-axis, Y-axis and x=2 (in Sq. units) is (A) 313 (B) 4 (C) 6 (D) 215
›Reveal solutionSolution
Area =∫02(x2+1)dx−∫12x−1dx=314−32=4 sq. units.
The two curves are:
- y=x2+1 — an upward parabola, vertex (0,1); at x=2, y=5.
- x=y2+1, i.e. y=x−1 — a rightward parabola through (1,0) and (2,1).
The region is bounded above by y=x2+1, on the left by the Y-axis, on the right by x=2, below by the X-axis for 0≤x≤1 and by y=x−1 for 1≤x≤2.
Area under the top curve from x=0 to 2:
∫02(x2+1)dx=[3x3+x]02=38+2=314. …
- TG EAPCET 2023Set eng-2023-05-14-FN1 markMCQQ.If the points of intersection of the parabolas y2=5x and x2=5y lie on the line L, then the area of the triangle formed by the directrix of one parabola, latus rectum of another parabola and the line L is (A) 3215 (B) 2512 (C) 825 (D) 3225
›Reveal solutionSolution
The two parabolas meet on the line L:y=x. The directrix of one, the latus rectum of the other, and L form a right triangle with both legs 25, so its area is 825.
Step 1 — line L. Solving y2=5x and x2=5y: substituting x=5y2 gives y4=125y, so y=0 or y=5, i.e. intersections (0,0) and (5,5). Thus L:y=x.
Step 2 — directrix and latus rectum. Each parabola has 4a=5, so a=45.
- For y2=5x: directrix x=−45; latus rectum x=45.
- For x2=5y: directrix y=−45; latus rectum y=45.
Take the directrix of the first, x=−45, and the latus rectum of the second, y=45 (any one-from-each choice gives the same area by symmetry).
Step 3 — vertices.
- x=−45∩y=x:(−45,−45) …
- TG EAPCET 2022Set eng-2022-07-18-FN1 markMCQQ.The area of the triangle formed by the tangent and the normal drawn to the curve y2=4x at (1,2) with Y-axis is (in square units) (A) 4 (B) 3 (C) 2 (D) 1
›Reveal solutionSolution
The area is found by computing the intercepts of the tangent and normal lines with the Y‑axis, then using the triangle’s base (distance between intercepts) and height (x‑coordinate of the point). The result is 3 square units.
We are given the parabola y2=4x and the point (1,2). The tangent and normal at this point, together with the Y‑axis, form a triangle. The Y‑axis is the line x=0, so the triangle’s vertices are: the intersection of the tangent with the Y‑axis, the intersection of the normal with the Y‑axis, and the point of tangency (1,2). The base of the triangle lies along the Y‑axis, and the height is the horizontal distance from the point to the Y‑axis (which is simply the x‑coordinate of the point).
Why this approach works: Instead of finding all three vertices and using a determinant, we can note that the Y‑axis is vertical, so the triangle’s base is the segment between the two Y‑intercepts. The height is the perpendicular distance from the point to the Y‑axis, which is just ∣x∣=1. Then area = 21×base×height.
- Find the equation of the tangent. For the parabola y2=4x, the standard tangent at (x1,y1) is yy1=2(x+x1). Here (x1,y1)=(1,2), so:
y⋅2=2(x+1)⇒2y=2x+2⇒y=x+1.
The Y‑intercept (set x=0) is y=1. So the tangent meets the Y‑axis at A(0,1).
- Find the equation of the normal. The slope of the tangent is 1 (from y=x+1). The slope of the normal is the negative reciprocal: −1. Using point-slope form at (1,2):
y−2=−1(x−1)⇒y−2=−x+1⇒y=−x+3.
The Y‑intercept (set x=0) is y=3. So the normal meets the Y‑axis at B(0,3).
- Determine the base of the triangle. The base is the segment AB on the Y‑axis from y=1 to y=3. Its length is:
base=∣3−1∣=2.
- Determine the height. …
- TG EAPCET 2026Set eng-2026-05-09-FN1 markMCQQ.The area of the region bounded by the curve y=∣x−2∣+∣x−8∣, X-axis and the lines x=0, x=10 is (A) 50 (B) 68 (C) 100 (D) 98
›Reveal solutionSolution
The area is found by splitting the absolute-value expression into linear pieces over intervals where the signs of the terms are constant, then integrating the resulting piecewise linear function from 0 to 10. The total area is 68, so the correct option is (B).
Concept & Intuition
The function y=∣x−2∣+∣x−8∣ is a sum of two absolute values. Each absolute value changes slope at its “corner” (where the inside is zero). So the whole function is piecewise linear, with possible corners at x=2 and x=8. Instead of integrating an absolute value directly, we break the domain [0,10] into subintervals where the expressions inside the absolute values have constant sign. On each subinterval, the absolute values become simple linear expressions, and the area under the curve (above the X‑axis) is just the integral of that linear function. Since the curve is always non‑negative, the area is exactly the definite integral from 0 to 10.
Step‑by‑step solution
- Identify the critical points The expressions inside the absolute values are zero at x=2 and x=8. These split the real line into three intervals:
(−∞,2),[2,8),[8,∞).
Our integration limits are x=0 to x=10, so we consider the subintervals [0,2], [2,8], and [8,10].
-
Write the function without absolute values on each subinterval
- On [0,2]: x−2≤0 so ∣x−2∣=−(x−2)=2−x. x−8<0 so ∣x−8∣=−(x−8)=8−x. Hence
y=(2−x)+(8−x)=10−2x.
- On [2,8]: x−2≥0 so ∣x−2∣=x−2. x−8≤0 so ∣x−8∣=8−x. Hence
y=(x−2)+(8−x)=6.
- On [8,10]: x−2>0 so ∣x−2∣=x−2. x−8≥0 so ∣x−8∣=x−8. Hence
y=(x−2)+(x−8)=2x−10.
- Integrate piecewise from 0 to 10
Area=∫02(10−2x)dx+∫286dx+∫810(2x−10)dx.
- First integral:
- TG EAPCET 2025Set eng-2025-05-02-AN1 markMCQQ.The area of the region bounded by the curves y=x3, y=x2 and the lines x=0 and x=2 is (A) 34 (B) 23 (C) 32 (D) 35
›Reveal solutionSolution
Area =23 sq. units — option (B).
Compare the curves: on [0,1], x2≥x3; on [1,2], x3≥x2. So
Area=∫01(x2−x3)dx+∫12(x3−x2)dx.
∫01(x2−x3)dx=31−41=121, …
- TG EAPCET 2023Set eng-2023-05-12-AN1 markMCQQ.The area (in sq. units) bounded by the curve y=2x−x2 and the line y=−x is (A) 29 (B) 211 (C) 316 (D) 522
›Reveal solutionSolution
The area between the parabola y=2x−x2 and the line y=−x is found by integrating the difference of the functions between their intersection points. The result is 29, so the correct option is (A).
We want the area bounded by a downward-opening parabola and a straight line. The key idea: area between two curves is the integral of (top function minus bottom function) over the interval where they cross. So first, find where they intersect; then decide which curve is above the other; then integrate.
-
Find intersection points
Set 2x−x2=−x.
Bring all terms to one side:
2x−x2+x=0⇒3x−x2=0
Factor: x(3−x)=0
So x=0 and x=3.
These are the boundaries of the region.
-
Determine which curve is on top
Pick a test point between 0 and 3, say x=1:
- Parabola: y=2(1)−12=1
- Line: y=−1 Since 1>−1, the parabola is above the line on (0,3). So the vertical height between them is (2x−x2)−(−x)=2x−x2+x=3x−x2.
-
Set up the definite integral
Area =∫03(3x−x2)dx …
-
- TG EAPCET 2022Set eng-2022-07-19-FN1 markMCQQ.Let P(4π),Q(45π),R(43π),T(47π) be the points on the hyperbola x2−4y2−4=0 in the parametric form. Then the area of the quadrilateral PQRT is (in square units) (A) 42 (B) 162 (C) 322 (D) 82
›Reveal solutionSolution
The quadrilateral is a rectangle whose sides are aligned with the asymptotes of the hyperbola. Its area is 82 square units, option (D).
The hyperbola is x2−4y2=4, which we rewrite in standard form:
4x2−1y2=1.
Its standard parametric form is x=2secθ, y=tanθ. The given points use parameters 4π,45π,43π,47π — these are spaced by 2π in the parameter. That spacing is the key: on a rectangular hyperbola, equal parametric spacing often gives a rectangle, but here the hyperbola is not rectangular (a=b). Still, the geometry of the secant/tangent parametrization creates a special shape.
Let’s find the coordinates.
-
Compute the four points.
For θ=4π:
x=2sec4π=2⋅2=22,
y=tan4π=1.
So P=(22,1).
For θ=45π:
sec45π=sec(π+4π)=−sec4π=−2,
tan45π=tan(π+4π)=tan4π=1.
So Q=(−22,1).
For θ=43π:
sec43π=sec(π−4π)=−sec4π=−2,
tan43π=tan(π−4π)=−tan4π=−1.
So R=(−22,−1).
For θ=47π:
sec47π=sec(2π−4π)=sec4π=2,
tan47π=tan(2π−4π)=−tan4π=−1.
So T=(22,−1).
-
Identify the shape.
The four points are:
P(22,1),Q(−22,1),R(−22,−1),T(22,−1).
These are the vertices of a rectangle centered at the origin, with sides parallel to the axes. …
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- TG EAPCET 2026Set eng-2026-05-09-AN1 markMCQQ.The area of the region bounded by the curves y=x2−3x+3 and y=2x2−1 is (A) 6403 (B) 27 (C) 19 (D) 6125
›Reveal solutionSolution
The region is bounded by two parabolas; find their intersection points, determine which curve is on top, then integrate the difference of the functions. The area is 6125, which corresponds to option (D).
The problem asks for the area between two curves. The core idea is always the same: area between curves is the integral of (top function minus bottom function) over the interval where they cross. But the real work is in finding where they intersect and which one lies above the other.
We have y=x2−3x+3 (call it f(x)) and y=2x2−1 (call it g(x)). Both are upward-opening parabolas. The first has vertex at x=1.5, the second at x=0. They will cross at two points, enclosing a finite region.
- Find the intersection points. Set f(x)=g(x):
x2−3x+3=2x2−1
Bring all terms to one side:
0=2x2−1−x2+3x−3=x2+3x−4
So x2+3x−4=0. Factor:
(x+4)(x−1)=0
Hence x=−4 and x=1. These are the limits of integration.
- Determine which curve is on top in [−4,1]. Pick a test point between the intersections, say x=0:
f(0)=02−3(0)+3=3
g(0)=2(0)2−1=−1
Since 3>−1, f(x) is above g(x) throughout the interval. (Both are continuous parabolas crossing only at the endpoints, so the ordering cannot flip inside.)
- Set up the area integral. Area A=∫x=−41[f(x)−g(x)]dx:
f(x)−g(x)=(x2−3x+3)−(2x2−1)=−x2−3x+4
So
A=∫−41(−x2−3x+4)dx
- Integrate term by term.
∫(−x2)dx=−3x3,∫(−3x)dx=−23x2,∫4dx=4x
Thus
A=[−3x3−23x2+4x]−41
- Evaluate at the upper limit x=1:
−313−23(1)2+4(1)=−31−23+4
Convert to sixths: −62−69+624=613
- Evaluate at the lower limit x=−4: …
- TG EAPCET 2026Set eng-2026-05-10-FN1 markMCQQ.Area of the region bounded by the curves y=2x, y2=4x and the lines x=21, x=1 is (A) log22−2−34−2 (B) 34−2−log22−2 (C) 34+2−log22−2 (D) log22−2−34+2
›Reveal solutionSolution
The area is the difference between the integral of y=2x and the integral of y=2x (the upper branch of y2=4x) from x=1/2 to x=1, giving option (B).
The region is bounded by two curves and two vertical lines. The key is to see which curve lies above the other in the given interval. The curve y2=4x is a right-opening parabola; solving for y gives y=±2x. Since the region is bounded also by y=2x (which is always positive), we only consider the upper branch y=2x.
Between x=1/2 and x=1, we need to compare 2x and 2x. At x=1, 21=2 and 21=2, so they meet. At x=1/2, 21/2=2≈1.414 and 21/2=2/2=2≈1.414 — they also meet! So the two curves actually intersect at both endpoints. But between them, which is larger? Test a point, say x=3/4: 23/4=48≈1.68, while 23/4=3≈1.73. So 2x>2x in the interior. That means the parabola lies above the exponential curve in this interval.
Thus the area is the integral of (upper curve minus lower curve) from x=1/2 to x=1:
Area=∫1/21(2x−2x)dx
Now we compute step by step.
-
Integrate 2x.
Write 2x=2x1/2. Its antiderivative is 2⋅3/2x3/2=34x3/2.
-
Integrate 2x.
The antiderivative of ax is logaax. So ∫2xdx=log22x.
-
Evaluate the definite integral.
[34x3/2−log22x]1/21
At x=1: 34(1)3/2−log221=34−log22.
At x=1/2: 34(21)3/2−log221/2=34⋅221−log22=624−log22=322−log22. …
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