Across
1
Part of a circle's circumference
3
Number less than zero
7
Split into equal parts
9
Divisible by two
10
The number representing nothing
11
Three-sided polygon
12
Difference between highest and lowest values
Down
2
Rectangle with four equal sides
4
Space between two intersecting lines
5
Symbol representing unknown value
6
Number divisible only by 1 and itself
8
Result of multiplication
13
Closed shape with straight sides