JEE Main: Differentiation and How To Calculate ‘e’

JEE Main: Differentiation and How To Calculate ‘e’

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Ramraj SainiUpdated on 19 Apr 2024, 07:49 PM IST

We all have come across the number ‘e’ while studying logarithm and calculus. This number is an irrational number like π, and is called Euler’s Number. Its value is 2.71828… and this sequence of digits never ends. So, how can we find this number and what is so special about this number?

JEE Main: Differentiation and How To Calculate ‘e’
Exponential-graph(Image:Wikimedia commons)

A property that you must have studied in differentiation that stands out among all differentiation formulae is

\frac{d}{dx}e^x=e^x

So, the differentiation of the function f(x) = ex, is this function itself. This makes this function unique. We will be using this property to calculate the number ‘e’. So, in all the calculations below, we will not use ‘e’ directly.

Let us start with the differentiation of a general exponential function, f(x) = 2x.

Using First Principle of Differentiation, we know that the differentiation of a function f(x) is

f'(x)=\lim_{h\rightarrow 0}\frac{f(x+h)-f(x)}{h}

So, differentiation of f(x) = 2x will be

\\f'(x)=\lim_{h\rightarrow 0}\frac{2^{x+h}-2^x}{h}\\\\f'(x)=\frac{2^x.2^h-2^x}{h}\\\\f'(x)=2^x\lim_{h\rightarrow 0}\frac{2^h-1}{h}.......equation(1)

Now, when the value of the limit h→0 [(2h-1)/h] is calculated by putting different values of h that are very close to 0, we can see that the value of this expression approaches 0.693147…(Note that we are not directly using the value of this limit as ln(2), as the number ‘e’ and thus ln(x), which is log with the base ‘e’, is not yet known).

Also Read,

Let us see what values of [(2h-1)/h] we get by putting different values of h that are close to 0. We can use a calculator to find these values

When h = 0.001, [(2h-1)/h] = 0.6933…

When h = 0.0001, [(2h-1)/h] = 0.6931…

When h = 0.00000001, [(2h-1)/h] = 0.6931…

We can see that [(2h-1)/h] value approaches 0.6931…and hence

limit h→0 [(2h-1)/h]= 0.6931…

From equation (i):

f'(x) = 2x.(0.6931…)

So, differentiation of f(x) = 2x is of the form

f'(x) =  Some constant. f(x)

Now if we do the same procedure with f(x) = 4x

\\f'(x)=\lim_{h\rightarrow 0}\frac{4^{x+h}-4^x}{h}\\\\f'(x)=\frac{4^x.4^h-4^x}{h}\\\\f'(x)=4^x\lim_{h\rightarrow 0}\frac{4^h-1}{h}.......equation(2)

When h = 0.001, [(4h-1)/h] = 1.3872…..

When h = 0.0001, [(4h-1)/h] = 1.38631…

When h = 0.00000001, [(4h-1)/h] = 1.38629…

So, limit h→0 [(4h-1)/h] = 1.38629…

And from (ii),

f'(x) =  4x . (1.38629…)

So, differentiation of f(x) = 4x is again of the form

f'(x) =  Some constant. f(x)

In fact, we can do the same exercise for any positive real number a, and we will find that the differentiation of f(x) = ax equals some constant times ax

It can also be seen that the value of this constant keeps on increasing as the value of ‘a’ increases. For example

For a = 2, the constant we calculated was 0.6931…

For a = 4, the constant we calculated was 1.38629…

Similarly, for a = 5, the constant can be calculated to be 1.6094…

For a = 6, the constant is 1.7917…

So naturally we can ask ourselves the question that can we find a number ‘a’ for which this constant value equals 1, and thus differentiation of ax is 1. ax, meaning that the differentiation of the function ax is this function itself ( = ax)

After doing multiple hits and trials, this number can be found to be 2.71828. That is why we have the unique property,

d/dx(ex)= ex

Euler’s Number also finds applications in fields of mathematics other than calculus. One of the most important applications is in Complex Numbers. You must have come across the relation eiπ = - 1. Imaginary powers of e help us get the values of many trigonometric series which would otherwise be very difficult to prove using only the trigonometric relations. The number is also used in Finance (to calculate compound interest), to explain population growth of humans or microbes, to explain radioactive decay (which in turn is used to tell the age of ancient objects), etc.

Due to numerous applications, ‘e’ is the second most famous mathematical constant after π. We also celebrate ‘e-day’ on 7 February. This date is chosen as it is written as 2/7 in month/date format and the digits 2,7 represent the first two digits used in the value of ‘e’ (2.71…).

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From the below website you can get the information regarding JEE Mains 2026 syllabus.

https://engineering.careers360.com/articles/jee-main-syllabus-2026

You can also visit the official website of NTA to know the syllabus.

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The registration form for JEE Main 2026 January session is expected to start in October 2025 (or first week of November) and the last date to submit is likely in November 2025.

Hope it helps !

After the 11th and 12th NCERT BOOKS. the best reference books available to students for the JEE main are-

Physics: for quality problems - HC verma(vol1&2) , for practice problems IE irodov, for various other derivations and theories - DC pandey.

Chemistry: Physical chemistry - RC MUKHERJEE practice problems.

OP tandon for Organic chemistry, JD lee for inorganic chemistry.


Mathematics: RD Sharma for the basics of every topic.


The above list is just an aggregate of the standard books. Choosing them depends of your personal preference equally. However, to get a detailed overview about any books related to JEE mains, you can follow the link below.

https://engineering.careers360.com/articles/best-books-for-jee-main

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You can download PDFs for any entrance exam by visiting Careers360.com, visiting the school section, and under that searching for your exam type. You will find all the related study material there, and you can practice from there. Practice is important for any entrance exams, so just start preparing, and all the best.

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If you're preparing for JEE Mains, it's smart to focus on high-weightage topics from both 11th and 12th. In Physics, give time to Thermodynamics, Current Electricity, and Modern Physics. For Maths, focus on Calculus, Vectors & 3D, and Probability—they often carry good marks. In Chemistry, master Organic Chemistry, Coordination Compounds, and Chemical Bonding. These topics are not just about scoring, but also concept-based, so practice well. Use NCERT for Chemistry—it’s gold. Solve previous year papers to spot patterns. And most importantly, stay consistent and don’t ignore your weak areas.