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JEE Maths
Class 12 Chapter 8

Must-Revise Concepts

Area Between Two Curves Calculus

Area of Hollow Cylinder

Area of Isosceles Triangle

Area Under The Curve

Area of Sector

Class 12 Maths Chapters List:- JEE & NEET Revision Notes

Chapter 1 Relations and Functions

Chapter 2 Inverse Trigonometric Functions

Chapter 3 Matrices

Chapter 4 Determinants

Chapter 5 Continuity and Differentiability

Chapter 6 Application of Derivatives

Chapter 7 Integrals

Chapter 8 Application of Integrals

Chapter 9 Differential Equations

Chapter 10 Vector Algebra

Chapter 11 Three Dimensional Geometry

Chapter 12 Linear Programming

Chapter 13 Probability

Frequently Asked Questions

The Application of Integrals chapter explains how definite integrals are used to calculate the area enclosed by curves, straight lines, and other graphical regions.

Drawing the graph helps identify the region enclosed, intersection points, and the correct upper and lower curves, reducing calculation errors.

The area under a curve is measured between a curve and an axis, whereas the area between two curves is calculated using the difference between the two functions over a given interval.

Applications of integrals are used in engineering, architecture, physics, economics, and computer graphics to calculate areas, volumes, and accumulated quantities.

It is a high-scoring Calculus chapter that frequently includes graph-based, conceptual, and numerical problems involving definite integrals and area calculations.

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Class 12 Maths Chapter 8: Application of Integrals

The Application of Integrals chapter extends the concept of definite integration to solve geometrical problems involving the area enclosed by curves. It focuses on calculating the area bounded by straight lines, curves, and combinations of both using definite integrals. This chapter plays a significant role in CBSE Board, JEE Main, and JEE Advanced, where students are expected to apply integration techniques to solve analytical and graphical problems accurately.

At ALLEN, Class 12 Maths Chapter 8 Application of Integrals smart study resources are designed to simplify the Application of Integrals through concise explanations, essential formulas, graphical interpretation, shortcut techniques, and exam-oriented practice. Class 12 Maths Chapter 8 notes help students strengthen conceptual understanding and improve problem-solving speed for both board and competitive examinations.

1.0Chapter Snapshot

Parameter

Details

Difficulty Level

Moderate

Revision Time

2–3 Hours

Key Concepts Covered

Area Under a Curve, Symmetry in Area Problems, Graphical Interpretation

2.0Chapter 8 Smart Study Material by ALLEN Experts: Download PDFs

Resource

Status

Chapter Mock Test Paper

Chapter Mock Test Paper Solution

On this page


  • 1.0Chapter Snapshot
  • 2.0Chapter 8 Smart Study Material by ALLEN Experts: Download PDFs

Application of Integrals 

Integrals are one of the most important concepts in calculus. The application of integrals class 12 includes calculating quantities that accumulate continuously, such as areas, volumes, work, energy, and probabilities. They help solve virtually all practical problems in varying fields, such as physics, economics, and biology.

1.0Application of Integrals in Maths

1. Finding the Area Under a Curve

The most common application of integrals is calculating the area under a curve. For a given function f(x), the area between the graph of the function and the x-axis over the interval [a,b] is determined using a definite integral:

 Area =∫ab​f(x)dx

This concept is used for finding the total area in many applications, such as in finding the distance traveled by an object moving along a path or to calculate the area between curves in geometry.

Example: Find the area under the curve

y=x2 from x=0 to x=2. 

Solution:

 Area =∫02​x2dx=[3x3​]02​=38​ square units 

2. Calculating the Area Between Two Curves

Many times, we need to calculate the area between two curves

y=f(x) and y=g(x), over an interval [a, b].  The area between the curves is found by subtracting the area under the lower curve from the area under the upper curve:

Area between curves =

∫ab​[f(x)−g(x)]dx

Example: Find the area between the curves

y=x2 and y=x from x=0 to x=1

Solution:

 Area =∫01​(x−x2)dx=[2x2​−3x3​]=21​−31​=61​

3. Finding the Average Value of a Function

The average value of a function f(x) over an interval [a, b][a, b][a, b] can be calculated using the formula:

Average value =

b−a1​∫ab​f(x)dx

This concept is used in many fields, like physics and economics, to determine the mean value of a quantity over time or space.

Example: Find the average value

f(x)=x2 over the interval [0,2].

Solution: Average value =

2−01​∫02​x2dx=21​[3x3​]=21​×38​

On this page


  • 1.0Application of Integrals in Maths
  • 1.11. Finding the Area Under a Curve
  • 1.22. Calculating the Area Between Two Curves
  • 1.33. Finding the Average Value of a Function

4. Applications in Probability

In probability theory, integrals are used to find probabilities for continuous random variables. It f(x) is the PDF or Probability Density Function of any random variable; the probability (P) that X lies in the interval [a, b] is : 

P(a≤X≤b)=∫ab​f(x)dx

Example: For a continuous random variable with the PDF,

f(x)=3x2,0≤x≤1, the probability that X lies between 0.5 and 1 is.

Solution:

P(0.5≤X≤1)=∫0.51​3x2dx=[x3]=1−0.125=0.875

1.0Application of integrals in Real life

1. Work Done by a Variable Force

Work is defined in physics as the force over a distance, and if the force is changing, then we make use of integrals to determine how much work gets done. The work formula is

W=∫ab​F(x)dx

Where function F(x) is the force applied at position x, and a and b are the limits of the distance over which the force acts?

Example: If a force

F(x)=2x( in newtons )is applied along a straight line from

x=0 to x=3, the work done.

Solution:

W=∫03​2xdx=[x2]03​=9 joules 

2. Finding the Volume of Solids

Integrals are also used to compute the volume of solids when the solids are of curved or irregular shapes. The volume of solids generated by revolving a region about an axis can be easily determined through techniques such as the disk/washer method or the shell method.

Disk Method

If a region is rotated around the x-axis, the volume of the solid formed is given by the formula:

V=2π∫ab​x⋅f(x)dx

Example (Disk Method): Find the volume (V) of the solid formed by rotating the specific region bounded by the

curvey=x2andthex−axisbetweenx=0 and x=1.

Solution:

v=π∫01​(x2)2dx=π∫01​x4dx=π[5x5​]=5π​

1.0Learning Outcomes

After completing this chapter, you will be able to:

  • Calculate the area under a curve using definite integrals.
  • Find the area enclosed between two curves.
  • Identify upper and lower functions correctly.
  • Apply properties of definite integrals to simplify calculations.
  • Solve graph-based area problems efficiently.
  • Interpret geometrical regions represented by equations.
  • Solve JEE Main, JEE Advanced, and CBSE Board questions confidently.

2.05-Minute Quick Revision

Must-Revise Concepts

  • Area Under a Curve
  • Area Between Two Curves
  • Area Bounded by Lines
  • Area in Different Intervals
  • Definite Integral Properties
  • Upper Curve and Lower Curve
  • Curves Intersecting at Multiple Points
  • Symmetry in Area Problems
  • Graphical Interpretation
  • Geometrical Applications of Integration

Important Formula Recall

  • Area under a curve: A=∫ab​f(x),dx
  • Area between two curves: A=∫ab​[f(x)−g(x)]dx
  • Area with respect to y-axis: A=∫cd​[x2​−x1​]dy

Important Properties / Shortcut Tips

  • Always sketch the graph before evaluating the integral.
  • Identify the upper and lower curves correctly.
  • Split the region into separate intervals if curves intersect.
  • Use symmetry whenever applicable to reduce calculations.
  • Ensure the calculated area is always positive.

3.0High Weightage Topics

Topic

JEE Importance

Difficulty Level

Area Under a Curve

High

Easy–Moderate

Area Between Two Curves

Very High

Moderate

Area with Respect to y-axis

High

Moderate

Graph-Based Area Problems

Very High

Moderate–High

Symmetry in Area Problems

High

Moderate

Mixed Area Problems

Very High

High

4.0Formula Handbook

Available soon

5.0Common Mistakes & JEE Tips

Common Mistake

Correct Approach

Not drawing the graph

Always sketch the curves before integrating.

Choosing the wrong upper or lower curve

Compare the functions over the given interval.

Ignoring intersection points

Find all points of intersection before calculating the area.

Obtaining negative area

Area is always positive; use the appropriate function order.

Using incorrect limits

Determine limits from the graph or intersection points.

Applying wrong variable of integration

Integrate with respect to the variable specified in the problem.

Missing interval division

Split the integral when the curves interchange positions.

6.0ALLEN Faculty Tips

  • Begin every problem by sketching the graph.
  • Learn standard curve shapes thoroughly.
  • Practice identifying the upper and lower functions quickly.
  • Revise the properties of definite integrals before solving area problems.
  • Focus on graph-based JEE questions regularly.
  • Solve Previous Years' Questions (PYQs) to improve accuracy and speed.

7.0PYQ Trend Analysis

Application of Integrals is an important Calculus chapter in JEE Main, JEE Advanced, and CBSE Board examinations. Questions are primarily based on graph interpretation, area under curves, and area enclosed between different functions.

Note: The trend below is based on the analysis of previous years' JEE Main and JEE Advanced question papers. The exact number of questions may vary each year.

Topic

Questions Asked (Last 5 Years)

Average Difficulty

Area Under Curve

1

Easy–Moderate

Area Between Curves

1–2

Moderate

Graph-Based Problems

1–2

Moderate

Symmetry-Based Questions

1

Moderate

Mixed Application Problems

1

Moderate–High

8.0Most Common Question Types

  • Finding the area enclosed between two curves.
  • Calculating the area under a given curve.
  • Determining the area using integration with respect to y.
  • Solving graph-based area problems.
  • Applying symmetry properties to simplify calculations.
  • Finding regions enclosed by straight lines and curves.
  • Solving mixed application problems involving multiple functions.

9.0Smart Revision Strategy

  1. Revise the properties of definite integrals.
  2. Practice sketching standard graphs.
  3. Learn to identify upper and lower curves correctly.
  4. Solve area under curve problems.
  5. Practice area between two curves.
  6. Revise symmetry-based shortcuts.
  7. Solve Previous Years' Questions (PYQs).
  8. Finish with a chapter-wise mock test.

On this page


  • 1.0Learning Outcomes
  • 2.05-Minute Quick Revision
  • 2.1Must-Revise Concepts
  • 2.2Important Formula Recall
  • 2.3Important Properties / Shortcut Tips
  • 3.0High Weightage Topics
  • 4.0Formula Handbook
  • 5.0Common Mistakes & JEE Tips
  • 6.0ALLEN Faculty Tips
  • 7.0PYQ Trend Analysis
  • 8.0Most Common Question Types
  • 9.0Smart Revision Strategy