Real Numbers
Real Numbers are just numbers like:
1 | 12.38 | -0.8625 | 3/4 | √2 | 1998 |
In fact:
Nearly any number you can think of is a Real Number
Real Numbers include:
Whole Numbers (like 0,1,2,3,4, etc) | |
Rational Numbers (like 3/4, 0.125, 0.333..., 1.1, etc ) | |
Irrational Numbers (like π, √3, etc ) |
Real Numbers can also be positive, negative or zero.
So ... what is NOT a Real Number?
√-1 (the square root of minus 1) is not a Real Number, it is an Imaginary Number | |
Infinity is not a Real Number | |
And there are also some special numbers that mathematicians play with that are not Real Numbers |
Why are they called "Real" Numbers?
Because they are not Imaginary Numbers.
The Real Numbers did not have a name before Imaginary Numbers were thought of. They got called "Real" because they were not Imaginary. That is the actual answer!
The Real Number Line
A point is chosen on the line to be the "origin", points to the right will be positive, and points to the left will be negative.
A distance is chosen to be "1", and whole numbers can then be marked off: {1,2,3,...}, and also in the negative direction: {-1,-2,-3, ...}
Any point on the line is a Real Number:
- The numbers could be rational (like 20/9)
- or irrational (like π)
But you won't find Infinity, or an Imaginary Number.