Across
1
Rectangular array of numbers
4
Number that divides evenly into another
6
Reference line in a graph
8
Symbol representing unknown value
12
Line crossing from corner to corner
13
The number representing nothing
Down
2
Exact correspondence on both sides
3
Repeated addition
5
Three-sided polygon
7
Part of a circle's circumference
9
Line touching circle at one point
10
Number greater than zero
11
System of ordered marks for measuring