Integration — KCSE Mathematics

KCSE Mathematics · 92 practice questions · 3 syllabus objectives · 3 revision lessons

32 easy28 medium32 hard

Last updated · Aligned to the KNEC KCSE syllabus

What You'll Learn

Key learning outcomes for this topic, aligned to the KNEC KCSE syllabus.

Interpret integration as the reverse process of differentiation and integrate polynomials

Evaluate definite integrals and apply integration in finding the area under a curve

Apply integration in kinematics to find displacement and velocity from acceleration

Revision Notes

Concise lesson notes for Integration, written to the KCSE Mathematics marking standard. Read the first lesson free below.

Understanding Integration and Polynomials

Integration is the reverse process of differentiation. When you differentiate a function, you find its rate of change. Conversely, integration helps you find the original function from its derivative. For polynomials, integration involves adding 1 to the exponent and dividing by the new exponent.

Steps to integrate a polynomial:

  1. Identify the polynomial to integrate, for example, ( f(x) = ax^n ).
  2. Apply the integration rule: ( \int ax^n , dx = \frac{a}{n+1} x^{n+1} + C ), where ( C ) is the constant of integration.
  3. Simplify the expression if necessary.

Example: Integrate ( 3x^2 ).

  • Solution: ( \int 3x^2 , dx = \frac{3}{2 + 1} x^{2 + 1} + C = x^3 + C ).

This means the integral of ( 3x^2 ) is ( x^3 + C ). Remember, practicing various polynomial integrations will enhance your understanding and speed in solving problems.

Key points to remember

  • Integration reverses differentiation to find original functions.
  • Integrate polynomials by increasing the exponent by one.
  • Divide the coefficient by the new exponent.
  • Always add the constant of integration, C.
  • Practice with different polynomial forms for mastery.

Worked example

Integrate ( 5x^3 ).

  • Solution: ( \int 5x^3 , dx = \frac{5}{3 + 1} x^{3 + 1} + C = \frac{5}{4} x^4 + C. )

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More lessons in this topic

Lesson 2: Evaluating Definite Integrals for Area

Objective: Evaluate definite integrals and apply integration in finding the area under a curve

To evaluate definite integrals, we use the Fundamental Theorem of Calculus. This theorem states that if ( F(x) ) is an antiderivative of ( f(x) ), then:

[ \int_{a}^{b} f(x) , dx = F(b) - F(a) ]

To find the area under a curve, we compute the definite integral of the function over the given interval. Here’s how to approach it:

  1. Determine the function ( f(x) ).
  2. Find the antiderivative ( F(x) ).
  3. Substitute the limits into ( F(x) ).
  4. Calculate ( F(b) - F(a) ).

Example: Evaluate ( \int_{1}^{3} (2x + 1) , dx ).

  1. The function is ( f(x) = 2x + 1 ).
  2. The antiderivative is ( F(x) = x^2 + x ).
  3. Substitute the limits:
    • ( F(3) = 3^2 + 3 = 12 )
    • ( F(1) = 1^2 + 1 = 2 )
  4. Calculate the area:
    • ( F(3) - F(1) = 12 - 2 = 10 )

Thus, the area under the curve from 1 to 3 is 10 square units.

  • Definite integrals find the area under a curve.
  • Use the Fundamental Theorem of Calculus for evaluation.
  • Calculate antiderivatives before applying limits.
  • Subtract the values at the upper and lower limits.

Evaluate ( \int_{0}^{2} (3x^2) , dx ). The antiderivative is ( F(x) = x^3 ). Thus, ( F(2) - F(0) = 8 - 0 = 8 ). The area is 8 square units.

Lesson 3: Integration in Kinematics

Objective: Apply integration in kinematics to find displacement and velocity from acceleration

In kinematics, integration is used to find displacement and velocity from acceleration. When you have the acceleration function, integrating it gives you the velocity function, and integrating the velocity function gives you the displacement function.

Key Steps:

  • Identify the acceleration function, a(t).
  • Integrate a(t) to find the velocity, v(t):
    • v(t) = ∫a(t) dt + C, where C is the constant of integration.
  • Integrate v(t) to find the displacement, s(t):
    • s(t) = ∫v(t) dt + D, where D is another constant of integration.

Example: Suppose the acceleration of an object is given by a(t) = 6t.

  1. To find velocity, integrate:
    • v(t) = ∫6t dt = 3t² + C.
  2. To find displacement, integrate:
    • s(t) = ∫(3t² + C) dt = t³ + Ct + D.

Remember to apply initial conditions to find the constants C and D if they are provided.

  • Integration of acceleration gives velocity function.
  • Integration of velocity gives displacement function.
  • Constants of integration represent initial conditions.

Given a(t) = 4t, find v(t) and s(t).

  • v(t) = ∫4t dt = 2t² + C.
  • s(t) = ∫(2t² + C) dt = (2/3)t³ + Ct + D.

Sample Questions

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1
easySHORT ANSWER3 marks

A vehicle accelerates from rest with an acceleration given by a(t) = 3t - 2. Determine the expression for the velocity v after time t. (3 marks)

Answer & marking scheme

Part (a) — 3 marks
Integrate: v = 3t²/2 - 2t + c (1 mk)
At t = 0, v = 0: c = 0 (1 mk)
Velocity expression: v = 3t²/2 - 2t (1 mk)
2
easySHORT ANSWER3 marks

Evaluate the definite integral: ∫ from 1 to 3 (4x + 2) dx and interpret the result in the context of finding the area under the curve. (3 marks)

Answer & marking scheme

Part (a) — 2 marks
Integrate: 2x² + 2x; (1 mk)
Evaluate at upper limit x = 3 and lower limit x = 1; (1 mk)
Part (b) — 1 mark
The result represents the area under the curve from x = 1 to x = 3. (1 mk)
3
easySHORT ANSWER3 marks

Define the integral of the polynomial function f(x) = 4x^3 - 2x^2 + 5. (3 marks)

Answer & marking scheme

Part (a) — 3 marks
Integrate 4x^3 to get x^4; result is x^4 (1 mk)
Integrate -2x^2 to get -2/3x^3; result is -2/3x^3 (1 mk)
Integrate 5 to get 5x; result is 5x + C (1 mk)
4

State the integral of the polynomial function 5x^3 - 4x^2 + 2 with respect to x. (3 marks)

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Frequently asked questions

What does the KCSE Mathematics topic "Integration" cover?

Reverse differentiation; indefinite and definite integrals; area under a curve; applications in kinematics

How many practice questions are available for Integration?

HighMarks has 92 Integration practice questions for KCSE Mathematics, each with a full marking scheme. The first 3 are free; sign up to access the rest, plus all KCSE mock exams and past papers.

Are these aligned with the KNEC KCSE syllabus?

Yes. Every objective on this page is taken directly from the official KNEC KCSE Mathematics syllabus. Practice questions match the KCSE exam format and are graded against the standard KNEC marking scheme.

How should I revise Integration for the KCSE exam?

Start with the revision notes on this page to refresh the core concepts, then work through the practice questions in increasing difficulty. Sign up for HighMarks to get a personalised study plan that adapts to the topics you keep getting wrong, plus mock exams, subject-wide practice, and detailed performance tracking. See pricing.

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