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ECET 2026 Preparation

Day 27 – Morning Session: Differentiation – Basic Derivatives – ECET 2026 CSE

Differentiation is one of the most important topics in Engineering Mathematics. ECET 2026 students can expect 2–3 direct questions from this chapter. If you master the basic derivative rules, you can solve even complex calculus problems easily.


📘 Concept Notes – Differentiation

👉 Definition:
Differentiation is the process of finding the derivative of a function.
The derivative of a function measures the rate of change of the function with respect to its variable.

  • If y=f(x)y = f(x)y=f(x), then derivative is written as:
    \frac{dy}{dx} or f'(x).

⚙️ Basic Derivative Rules

  1. Power Rule:
    \frac{d}{dx}(x^n) = n x^{n-1}
    Example: \frac{d}{dx}(x^5) = 5x^4
  2. Constant Rule:
    \frac{d}{dx}(c) = 0
    Example: \frac{d}{dx}(7) = 0
  3. Constant × Function Rule:
    \frac{d}{dx}[c \cdot f(x)] = c \cdot f'(x)
    Example: \frac{d}{dx}[4x^3] = 12x^2
  4. Sum Rule:

\frac{d}{dx}[f(x) + g(x)] = f'(x) + g'(x)

Difference Rule:

\frac{d}{dx}[f(x) - g(x)] = f'(x) - g'(x)

Exponential Function:
\frac{d}{dx}[e^x] = e^x

\frac{d}{dx}[a^x] = a^x \ln a

Logarithmic Function:

\frac{d}{dx}[\ln x] = \frac{1}{x}

Trigonometric Functions:

  • \frac{d}{dx}(\sin x) = \cos x
  • \frac{d}{dx}(\cos x) = -\sin x
  • \frac{d}{dx}(\tan x) = \sec^2 x
  • \frac{d}{dx}(\cot x) = -\csc^2 x
  • \frac{d}{dx}(\sec x) = \sec x \tan x
  • \frac{d}{dx}(\csc x) = -\csc x \cot x

✍️ Example Problems

Example 1:
Find derivative of y = x^3 + 2x^2 - 5x + 7.

Solution:

\frac{dy}{dx} = 3x^2 + 4x - 5


Example 2:
Find derivative of y = e^x + \ln x.

Solution:

\frac{dy}{dx} = e^x + \frac{1}{x}


Example 3:
Find derivative of y = \sin x + \cos x.

Solution:

\frac{dy}{dx} = \cos x - \sin x


🔟 10 Most Expected MCQs – ECET 2026

Q1. Derivative of x^5 is:
A) x^4
B) 5x^4
C) x^5
D) 6x^5

Q2. Derivative of a constant is:
A) 1
B) 0
C) Infinity
D) Same constant

Q3. \frac{d}{dx}(e^x) = ?
A) e^x
B) x e^x
C) \ln x
D) None

Q4. Derivative of \ln x is:
A) x
B) \frac{1}{x}
C) \ln e
D) e^x

Q5. \frac{d}{dx}(\sin x) = ?
A) \cos x
B) -\sin x
C) \tan x
D) \sec^2 x

Q6. \frac{d}{dx}(\cos x) = ?
A) \sin x
B) -\sin x
C) \tan x
D) \sec x \tan x

Q7. \frac{d}{dx}(\tan x) = ?
A) \cos^2 x
B) \sec^2 x
C) \sin^2 x
D) \csc^2 x

Q8. \frac{d}{dx}(a^x) = ?
A) a^x
B) a^x \ln a
C) \ln x
D) \ln a

Q9. \frac{d}{dx}(7x^2) = ?
A) 14x
B) 7x^2
C) 2x
D) x^7

Q10. Derivative of \csc x is:
A) -\csc x \cot x
B) \csc^2 x
C) \cot x
D) -\sec x \tan x


✅ Answer Key (Table)

Q.NoAnswer
Q1B
Q2B
Q3A
Q4B
Q5A
Q6B
Q7B
Q8B
Q9A
Q10A

🧠 Explanations of Answers

  • Q1 → B: Power rule → nx^{n-1}, so derivative of x^5 = 5x^4.
  • Q2 → B: Derivative of any constant is 0.
  • Q3 → A: Derivative of e^x is e^x.
  • Q4 → B: \frac{d}{dx}(\ln x) = \frac{1}{x}.
  • Q5 → A: Derivative of \sin x is \cos x.
  • Q6 → B: Derivative of \cos x is -\sin x.
  • Q7 → B: Derivative of \tan x is \sec^2 x.
  • Q8 → B: Derivative of a^x is a^x \ln a.
  • Q9 → A: Derivative of 7x^2 = 14x.
  • Q10 → A: Derivative of \csc x = -\csc x \cot x.

🎯 Why This Practice Matters for ECET 2026

Differentiation is a core part of Calculus. In ECET exams, questions are mostly direct formula-based, making them scoring topics. By memorizing and practicing basic derivatives, you can solve integration, maxima-minima, and applied problems faster.


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