Notations
Some reoccurring notations that IB assumes to be prior knowledge are listed below. Interpreting and using correct notations are assessed in all papers and in the internal assessment.
Contents
Interval notation
Interval notation is used only in HL papers, but it can be helpful to know in SL for more effective communication on the IA and exams.
means
means
means
means
Intervals using (positive or negative infinity) must use the exclusive notation, eg, or .
is the way to specify two non-overlapping intervals.
Sets of numbers
Here are some common sets.
symbol | name | description | examples |
---|---|---|---|
integers | multiples of | ||
positive integers | integers greater than | ||
negative integers | integers less than | ||
natural numbers | and positive integers | ||
rational numbers | ratios of integers | ||
real numbers | numbers on number line |
HL students should also recognize for complex numbers.
It is worth pointing out that and belong to none of the above sets. The real numbers is all numbers on the open interval, ie means .
Where is that bracket?
Generally speaking, an operator takes the first term as its argument.
Examples
- , formula for variance (HL)
- , this is super rare, but similar notations have appeared on exams.
If you want to apply an operator to an expression with addition or subtraction at the top level, be sure to use parentheses.
iff
iff, , means if and only if. means both if then , but also if then . So means they are both true or both false.
In contrast, means if is true then is also true, but it does not necessarily mean is true means is true.