Across
1
Line crossing from corner to corner
4
Collection of distinct elements
6
Total distance around a shape
7
Single numeral from 0 to 9
13
The number representing nothing
Down
2
Line touching circle at one point
3
Result of multiplication
5
Rectangle with four equal sides
8
Power to which a number is raised
9
Closed shape with straight sides
10
Value that does not change
11
Round shape with all points equidistant
12
Proven mathematical statement