Across
1
The number representing nothing
3
Space between two intersecting lines
5
Part of a circle's circumference
6
Steepness of a line
8
Line touching circle at one point
12
Lines that never intersect
13
Symbol representing unknown value
Down
2
Divisible by two
3
Math using letters for unknown values
4
Longest side of a right triangle
7
Comparison of two quantities
9
Number with digits after a point
10
Middle value in an ordered dataset
11
Repeated addition