Coordinate systems:
They are two mutually perpendicular coordinate lines which intersect in the origin O on each line.
The four quadrants in a coordinate system:
Quadrant I is the area where a>0 and b>0.
Quadrant II is the area where a<0 and b>0.
Quadrant III is the area where a<0 and b<0.
Quadrant IV is the area where a>0 and b<0.
Distance:
The distance between any two points is defined as:
.
Data sets:
The grouping or collection of similar or related data.
Subsets:
If A and B are sets and every element of A is also an element of B, then: A is a subset of B, denoted by
.
Product of two data sets:
If S and T are sets, the product set of S and T will be denoted by 
, which satisfies
.
Line:
A geometric figure formed by a point moving along a fixed direction and the reverse direction.
Slope of a line:
If 
and 
are arbitrary two points on the line, the slope can be calculated by
.
Midpoint of any two points:
The distance between two arbitrary points is given by
.
