Across
1
Symbol representing unknown value
4
Reference line in a graph
6
Part of a circle's circumference
7
Exact correspondence on both sides
8
The number representing nothing
9
Difference between highest and lowest values
Down
2
Lines that never intersect
3
Number with digits after a point
5
Round shape with all points equidistant
10
Number greater than zero
11
Power to which a number is raised