Across
1
Symbol representing unknown value
4
Rectangular array of numbers
5
Mathematical rule or equation
6
Three-sided polygon
7
Exact correspondence on both sides
8
Power to which a number is raised
Down
2
Lines that never intersect
3
Part of a whole number
6
Proven mathematical statement
9
Rectangle with four equal sides
10
Part of a circle's circumference
11
Part of a line with two endpoints
12
Line touching circle at one point
13
Number less than zero