Across
1
Value that does not change
7
Distance from center to edge of circle
8
Line touching circle at one point
9
Collection of distinct elements
10
Lines that never intersect
11
Number divisible only by 1 and itself
13
Number with digits after a point
Down
2
Number greater than zero
3
Part of a line with two endpoints
4
Reference line in a graph
5
Three-sided polygon
6
Power to which a number is raised
12
Exact correspondence on both sides