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
- 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