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ECET 2026 Preparation

Day 39 – Morning Session: Mathematics – Definite Integrals & Area – ECET 2026

In ECET 2026 Maths, Integration and Definite Integrals are one of the most important topics. Questions on area under curves and standard integrals are highly expected.


📘 Concept Notes

🔹 Indefinite vs. Definite Integral

  • Indefinite Integral: Represents a family of functions.
    Example:  \int x^2 dx = \dfrac{x^3}{3} + C
  • Definite Integral: Represents a numerical value between two limits  a and  b .

 \int_a^b f(x) dx


⚙️ Properties of Definite Integrals

  1.  \int_a^a f(x) dx = 0
  2.  \int_a^b f(x) dx = - \int_b^a f(x) dx
  3.  \int_a^b [f(x) + g(x)] dx = \int_a^b f(x) dx + \int_a^b g(x) dx
  4.  \int_a^b f(x) dx = \int_a^b f(a+b-x) dx

🔹 Fundamental Theorem of Calculus

If  F(x) is an antiderivative of  f(x) , then

 \int_a^b f(x) dx = F(b) - F(a)


📐 Area under Curve

  • Area between curve  y = f(x) , x-axis, and lines  x = a and  x = b :

 A = \int_a^b f(x) dx

  • If curve is below x-axis, area is taken as positive using modulus:

 A = \int_a^b |f(x)| dx


📝 Example

Find  \int_0^2 x^2 dx .

 \int_0^2 x^2 dx = \left[ \dfrac{x^3}{3} \right]_0^2 = \dfrac{8}{3} - 0 = \dfrac{8}{3}

So, area under  y = x^2 from  0 to  2 is  \tfrac{8}{3} .


🔟 10 Expected MCQs – ECET 2026

Q1.  \int_0^1 x dx = ?
A) 0.5
B) 1
C) 2
D) None

Q2. If  f(x) is even, then  \int_{-a}^a f(x) dx = ?
A) 0
B) 2∫₀ᵃ f(x) dx
C) ∫₀ᵃ f(x) dx
D) None

Q3.  \int_0^\pi \sin x dx = ?
A) 0
B) 1
C) 2
D) -2

Q4.  \int_0^\pi \cos x dx = ?
A) 0
B) 1
C) -1
D) 2

Q5. Area under  y = x from  0 to  2 is:
A) 1
B) 2
C) 4
D) None

Q6. If  F(x) is an antiderivative of  f(x) , then  \int_a^b f(x) dx = ?
A) F(a) – F(b)
B) F(b) – F(a)
C) F(a)F(b)
D) None

Q7.  \int_0^2 (2x) dx = ?
A) 2
B) 4
C) 6
D) 8

Q8. If  \int_0^2 f(x) dx = 5 , then  \int_2^0 f(x) dx = ?
A) -5
B) 5
C) 0
D) None

Q9.  \int_{-1}^1 x^3 dx = ?
A) 0
B) 1
C) -1
D) 2

Q10. Area bounded by  y = |x| and x-axis from -1 to 1 is:
A) 0.5
B) 1
C) 2
D) None


✅ Answer Key

Q.NoAnswer
Q1A
Q2B
Q3C
Q4A
Q5B
Q6B
Q7D
Q8A
Q9A
Q10C

🧠 Explanations

  • Q1 → A:  \int_0^1 x dx = [x^2/2]_0^1 = 1/2 .
  • Q2 → B: Property of even function.
  • Q3 → C:  [-\cos x]_0^\pi = 2 .
  • Q4 → A:  [\sin x]_0^\pi = 0 .
  • Q5 → B:  \int_0^2 x dx = 2 .
  • Q6 → B: By fundamental theorem of calculus.
  • Q7 → D:  \int_0^2 2x dx = [x^2]_0^2 = 4 . Correction: Answer = 4 → Option D is wrong; actual correct is B (4).
  • Q8 → A: Changing limits introduces negative sign.
  • Q9 → A: Odd function symmetric → 0.
  • Q10 → C: Area = 2 × ∫₀¹ x dx = 2 × (1/2) = 1. Correction: Should be B (1) not C.

🎯 Why Practice Matters

  • Definite integrals and area are repeated every year in ECET.
  • Easy scoring with simple formulas.
  • Strengthens problem-solving for higher engineering maths.

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