Across
1
Part of a circle's circumference
3
Lines that never intersect
4
Sum divided by count
5
Exact correspondence on both sides
6
Mathematical statement of equality
9
Single numeral from 0 to 9
11
Result of multiplication
12
The number representing nothing
Down
2
Round shape with all points equidistant
3
Total distance around a shape
7
Longest side of a right triangle
8
Middle value in an ordered dataset
9
Line crossing from corner to corner
10
Part of a line with two endpoints