Area under Curves – Tricks for Solving Area under Curves | Class 12 Math Notes Study Material Download Free PDF

Important Concepts on Area under the Curves

If the area under one curve and another curve can be found, then the area between the curves can be calculated.

Consider two curves to be y = f (x) and y = g (x) between the interval x = a to x = b is

\(\begin{array}{l}Area=\int_{a}^{b}|f(x)-g(x)dx\end{array} \)

  • The area of the ellipse = πab.
  • The shift in the coordinate axis leads to the area enclosed by a curve remaining invariant.
  • To check the symmetry of the curve following steps are followed:
  1. The curve is said to be symmetrical about the x-axis when y is changed to -y, and there is no change in the curve.
  2. The curve is said to be symmetrical about the y-axis when x is changed to -x, and there is no change in the curve.
  3. If the curve remains unchanged when x is changed to -x and y is changed to -y, then it is symmetrical to both axes.
  • If x is interchanged to y, resulting in no change of the curve, then it is symmetrical about the line y = x.

The standard steps that are followed in drawing the curve are as follows:

1) A check for symmetry is to be done.

  • Symmetry about the x-axis: The curve is symmetrical about the x-axis if the curve remains unchanged when y = -y.
  • Symmetry about the y-axis: The curve is symmetrical about the y-axis if the curve remains unchanged when x = -x.
  • Symmetrical about both axes: The curve is symmetrical about both axes if the curve remains unchanged when x = -x and y = -y.
  • Symmetrical about the line y = x: The curve is said to be symmetrical about the line y = x if the curve remains unchanged on interchanging x and y. 

2) The point of intersection of the axes is to be noted.
3) Find dy / dx to find stationary points. Find the intervals to determine whether the function is increasing or decreasing.

4) Find y when x → ∞ or -∞.

How to Find the Area under Curves

A few examples are illustrated below on finding areas enclosed by different curves.

Example 1: What is the area bounded by the curve y = log x, x−axis and the ordinates x = 1, x = 2?

Solution:

Given curve y = log x and x = 1, x = 2

Hence, the required area

\(\begin{array}{l}=\left[\int_{1}^{2}logxdx=(x\ logx-x)\right]_1^2\end{array} \)

= 2 log 2 − 1 = (log 4 − 1) sq. unit

Example 2: If the ordinate x = a divides the area bounded by the curve y = (1 + [8 / x2]), the x−axis and the ordinates x = 2, x = 4 into two equal parts, then what is the value of a?

Solution:

Let the ordinate at x = a divide the area into two equal parts.

\(\begin{array}{l}AMNB=\int_{4}^{2}=[1+\frac{8}{x^2}]dx=[x-\frac{8}{x}]{_{2}}^{4}=4\end{array} \)

and

\(\begin{array}{l}ACDM=\int_{2}^{a}=[1+\frac{8}{x^2}]dx=2\end{array} \)

On solving, we get a = ± 2√2

Since a > 0, a = 2√2

Example 3: If the area bounded by the curves y2 = 4ax and y = mx is a2 / 3, then find the value of m.

Solution:

The two curves y2 = 4ax and y = mx intersect at (4a / m2, 4a / m), and the area enclosed by the two curves is given by

\(\begin{array}{l}\int_{0}^{4a/m^2}[\sqrt{4ax-mx}]dx=\frac{a^2}{3}\end{array} \)

[8 / 3] * [a2 / m3] = a2/ 3

⇒ m3 = 8

⇒ m = 2

Example 4: Find the ratio of the areas bounded by the curves y = cos x and y = cos 2x between x = 0, x = π/3 and x−axis.

Solution:

\(\begin{array}{l}A_1=\int_{0}^{\pi/3}cos\ x\ dx=\frac{\sqrt{3}}{2}\end{array} \)

\(\begin{array}{l}A_2=\int_{0}^{\pi/3}cos\ 2x dx=\frac{\sqrt{3}}{4}\end{array} \)

Hence, the ratio is A1 : A2 = 2 : 1

Example 5: What is the area of the smaller part between the circle x2 + y2 = 4 and the line x = 1?

Solution:

Area of smaller part

\(\begin{array}{l}= 2\int_{1}^{2}\sqrt{4-x^2}dx=2[\frac{x}{2}\sqrt{4-x^2}+2sin^{-1}\frac{x}{2}]\end{array} \)

in the interval [1, 2]

\(\begin{array}{l}= 2[2*\frac{\pi}{2}-[\frac{\sqrt{3}}{2}-2*\frac{\pi}{6}]\end{array} \)

\(\begin{array}{l}= 2[\pi-[\frac{\sqrt{3}}{2}-\frac{\pi}{3}]\end{array} \)

\(\begin{array}{l}=\frac{8\pi}{3}-\sqrt{3}\end{array} \)

Example 6: What is the area in the first quadrant between x2 + y2 = π2 and y = sinx?

Solution:

The area of the circle in the first quadrant is π* (π2) / 4, i.e., π3 / 4.

Also, the area bounded by curve y = sinx and x-axis is 2 sq. unit.

Hence, the required area is [π3 / 4] − 2 = [π3 − 8] / 4

Example 7: The area enclosed by the curves y = sin x + cos x and y = |cos x – sin x| over the interval [0, π/2] is

Solution:

\(\begin{array}{l}y_{1}=sinx+cosx=\sqrt{2}sin(x+\frac{\pi}{4})\\ y_{2}=|sinx-cosx|=\sqrt{2}sin|sin\frac{\pi}{4}-x|\\ \text{Area}\ =\int_{0}^\frac{\pi}{4}[(sinx+cosx)-(cosx-sinx)]dx+\int_{\frac{\pi}{4}}^{\frac{\pi}{2}}[(sinx+cosx)-(sinx-cosx)]dx\\ =4-2\sqrt{2}\\ =2\sqrt{2}(\sqrt{2}-1)\end{array} \)

Example 8: Let g(x) = cos x2, f(x) = √x and α, β (α < β) be the roots of the quadratic equation 18x2 – 9πx + π2 = 0. Then, the area bounded by the curve y = (gof) (x) and the lines x = α, x = β and y = 0 is

Solution:

\(\begin{array}{l}18x^2-9\pi x+{\pi}^{2}=0 ; gof(x)=cosx\\(3x-\pi)(6x-\pi)=0\\\alpha =\frac{\pi}{6}, \beta =\frac{\pi}{3}\\A=\int_{\frac{\pi}{6}}^{\frac{\pi}{3}}cosxdx=\frac{\sqrt{3}-1}{2}\end{array} \)

Er. Neeraj K.Anand is a freelance mentor and writer who specializes in Engineering & Science subjects. Neeraj Anand received a B.Tech degree in Electronics and Communication Engineering from N.I.T Warangal & M.Tech Post Graduation from IETE, New Delhi. He has over 30 years of teaching experience and serves as the Head of Department of ANAND CLASSES. He concentrated all his energy and experiences in academics and subsequently grew up as one of the best mentors in the country for students aspiring for success in competitive examinations. In parallel, he started a Technical Publication "ANAND TECHNICAL PUBLISHERS" in 2002 and Educational Newspaper "NATIONAL EDUCATION NEWS" in 2014 at Jalandhar. Now he is a Director of leading publication "ANAND TECHNICAL PUBLISHERS", "ANAND CLASSES" and "NATIONAL EDUCATION NEWS". He has published more than hundred books in the field of Physics, Mathematics, Computers and Information Technology. Besides this he has written many books to help students prepare for IIT-JEE and AIPMT entrance exams. He is an executive member of the IEEE (Institute of Electrical & Electronics Engineers. USA) and honorary member of many Indian scientific societies such as Institution of Electronics & Telecommunication Engineers, Aeronautical Society of India, Bioinformatics Institute of India, Institution of Engineers. He has got award from American Biographical Institute Board of International Research in the year 2005.

CBSE Class 12 Maths Syllabus 2025-26 with Marks Distribution

The table below shows the marks weightage along with the number of periods required for teaching. The Maths theory paper is of 80 marks, and the internal assessment is of 20 marks which totally comes out to be 100 marks.

CBSE Class 12 Maths Syllabus And Marks Distribution 2023-24

Max Marks: 80

No.UnitsMarks
I.Relations and Functions08
II.Algebra10
III.Calculus35
IV.Vectors and Three – Dimensional Geometry14
V.Linear Programming05
VI.Probability08
Total Theory80
Internal Assessment20
Grand Total100

Unit-I: Relations and Functions

1. Relations and Functions

Types of relations: reflexive, symmetric, transitive and equivalence relations. One to one and onto functions.

2. Inverse Trigonometric Functions

Definition, range, domain, principal value branch. Graphs of inverse trigonometric functions.

Unit-II: Algebra

1. Matrices

Concept, notation, order, equality, types of matrices, zero and identity matrix, transpose of a matrix, symmetric and skew symmetric matrices. Operations on matrices: Addition and multiplication and multiplication with a scalar. Simple properties of addition, multiplication and scalar multiplication. Noncommutativity of multiplication of matrices and existence of non-zero matrices whose product is the zero matrix (restrict to square matrices of order 2). Invertible matrices and proof of the uniqueness of inverse, if it exists; (Here all matrices will have real entries).

2. Determinants

Determinant of a square matrix (up to 3 x 3 matrices), minors, co-factors and applications of determinants in finding the area of a triangle. Adjoint and inverse of a square matrix. Consistency, inconsistency and number of solutions of system of linear equations by examples, solving system of linear equations in two or three variables (having unique solution) using inverse of a matrix.

Unit-III: Calculus

1. Continuity and Differentiability

Continuity and differentiability, derivative of composite functions, chain rule, derivative of inverse trigonometric functions like sin-1 x, cos-1 x and tan-1 x, derivative of implicit functions. Concept of exponential and logarithmic functions.
Derivatives of logarithmic and exponential functions. Logarithmic differentiation, derivative of functions expressed in parametric forms. Second order derivatives.

2. Applications of Derivatives

Applications of derivatives: rate of change of quantities, increasing/decreasing functions, maxima and minima (first derivative test motivated geometrically and second derivative test given as a provable tool). Simple problems (that illustrate basic principles and understanding of the subject as well as real-life situations).

3. Integrals 

Integration as inverse process of differentiation. Integration of a variety of functions by substitution, by partial fractions and by parts, Evaluation of simple integrals of the following types and problems based on them.

Fundamental Theorem of Calculus (without proof). Basic properties of definite integrals and evaluation of definite integrals.

4. Applications of the Integrals

Applications in finding the area under simple curves, especially lines, circles/ parabolas/ellipses (in standard form only)

5. Differential Equations

Definition, order and degree, general and particular solutions of a differential equation. Solution of differential equations by method of separation of variables, solutions of homogeneous differential equations of first order and first degree. Solutions of linear differential equation of the type:

dy/dx + py = q, where p and q are functions of x or constants.

dx/dy + px = q, where p and q are functions of y or constants.

Unit-IV: Vectors and Three-Dimensional Geometry

1. Vectors

Vectors and scalars, magnitude and direction of a vector. Direction cosines and direction ratios of a vector. Types of vectors (equal, unit, zero, parallel and collinear vectors), position vector of a point, negative of a vector, components of a vector, addition of vectors, multiplication of a vector by a scalar, position vector of a point dividing a line segment in a given ratio. Definition, Geometrical Interpretation, properties and application of scalar (dot) product of vectors, vector (cross) product of vectors.

2. Three – dimensional Geometry

Direction cosines and direction ratios of a line joining two points. Cartesian equation and vector equation of a line, skew lines, shortest distance between two lines. Angle between two lines.

Unit-V: Linear Programming

1. Linear Programming

Introduction, related terminology such as constraints, objective function, optimization, graphical method of solution for problems in two variables, feasible and infeasible regions (bounded or unbounded), feasible and infeasible solutions, optimal feasible solutions (up to three non-trivial constraints).

Unit-VI: Probability

1. Probability

Conditional probability, multiplication theorem on probability, independent events, total probability, Bayes’ theorem, Random variable and its probability distribution, mean of random variable.

Students can go through the CBSE Class 12 Syllabus to get the detailed syllabus of all subjects. Get access to interactive lessons and videos related to Maths and Science with ANAND CLASSES’S App/ Tablet.

Frequently Asked Questions on CBSE Class 12 Maths Syllabus 2025-26

Q1

Is Calculus an important chapter in the CBSE Class 12 Maths Syllabus?

Yes, Calculus is an important chapter in the CBSE Class 12 Maths Syllabus. It is for 35 marks which means that if a student is thorough with this chapter will be able to pass the final exam.

Q2

How many units are discussed in the CBSE Class 12 Maths Syllabus?

In the CBSE Class 12 Maths Syllabus, about 6 units are discussed, which contains a total of 13 chapters.

Q3

How many marks are allotted for internals in the CBSE Class 12 Maths syllabus?

About 20 marks are allotted for internals in the CBSE Class 12 Maths Syllabus. Students can score it with ease through constant practice.