Disproof by Counter Example (OCR AS Maths: Pure)

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Disproof by Counter Example

What is disproof by counter-example?

  • Disproof by counter-examples involves finding a value that does not work for the given statement
    • That value is called a counter-example

How do I disprove a result?

  • You only need to find one value that does “not work”
  • Numbers that have unusual results are often helpful to try

 

Disproof by Counter example Notes Diagram, A Level & AS Level Pure Maths Revision Notes

 

  • Look carefully to see what types of number the result is claimed for – it may just be integers rather than real numbers
  • Irrational numbers can be unusual
  • Think about areas of maths where unusual things happen – such as in trigonometry where there are several angles with the same sine value

Worked example

Disproof by Counter-example Example, A Level & AS Level Pure Maths Revision Notes

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Paul

Author: Paul

Expertise: Maths

Paul has taught mathematics for 20 years and has been an examiner for Edexcel for over a decade. GCSE, A level, pure, mechanics, statistics, discrete – if it’s in a Maths exam, Paul will know about it. Paul is a passionate fan of clear and colourful notes with fascinating diagrams – one of the many reasons he is excited to be a member of the SME team.