Tangents, Normals And Rates Of Change
Overview
A tangent line just touches a curve at a single point, running in exactly the same direction as the curve at that instant. Its perpendicular partner, the normal, points straight into the curve. Together they unlock a family of problems that link algebra, coordinate geometry and calculus in a single question.
In this topic you will learn how to use differentiation to find the gradient of a curve at any point, build the equations of tangent and normal lines, and extend the chain rule to connected rates of change. You will also meet the small-change approximation, a powerful tool for estimating how a function responds to a tiny shift in its input.
Objectives
- Find the equations of tangents and normals to the curve y = f(x)
- Apply calculus to rates of change and connected rates of change
- Understand and use the approximation dy is approximately equal to (dy/dx) times dx for small dx
Mind map
This topic is mapped out so you can see how the ideas connect.
Open the mind map in the app
Flashcards
Quick recall practice on the facts this topic is tested on.
Practise these cards in the app
Lesson Note
Complete Note Available on the Green Bridge App
Get the Green Bridge CBT app on your phone or computer for the complete IGCSE library: past papers, mark schemes, mind maps, flashcards and audio lessons.
Lesson Evaluation
Congratulations on completing the lesson on Tangents, Normals And Rates Of Change. Now that youve explored the key concepts and ideas, its time to put your knowledge to the test. This section offers a variety of practice questions designed to reinforce your understanding and help you gauge your grasp of the material.
You will encounter a mix of question types, including multiple-choice questions, short answer questions, and essay questions. Each question is thoughtfully crafted to assess different aspects of your knowledge and critical thinking skills.
Use this evaluation section as an opportunity to reinforce your understanding of the topic and to identify any areas where you may need additional study. Don't be discouraged by any challenges you encounter; instead, view them as opportunities for growth and improvement.
- The curve y = x^2 + 3x passes through (1, 4). What is the gradient of the tangent at this point? A) 4 B) 5 C) 6 D) 7 Answer: B
- If the tangent to a curve at a point has gradient 4, what is the gradient of the normal? A) 4 B) -4 C) 1/4 D) -1/4 Answer: D
- The radius of a circle increases at 2 cm/s. Given A = pi r^2, what is dA/dt when r = 5? A) 10 pi B) 20 pi C) 25 pi D) 50 pi Answer: B
- For y = x^3, the small-change approximation gives delta y approximately equal to 3x^2 delta x. If x = 2 and delta x = 0.01, what is delta y approximately? A) 0.06 B) 0.12 C) 0.24 D) 0.36 Answer: B
- At a point on a curve, dy/dx = 0. What can you say about the normal at this point? A) It is horizontal B) It is vertical C) It has gradient 1 D) It does not exist Answer: B
Work through these questions in the app
Work through these questions in the app
Practice Mock Questions
Want to practice mock questions on Tangents, Normals And Rates Of Change? Download the Green Bridge CBT app to access mock questions and full practice assessments for this topic.
Download The App On Google Playstore
Everything you need to excel in your exams
