Across
1
Three-sided polygon
5
Part of a line with two endpoints
6
Number that divides evenly into another
7
Number less than zero
8
Result of addition
11
Divisible by two
12
Single numeral from 0 to 9
Down
2
Round shape with all points equidistant
3
Lines that never intersect
4
Symbol representing unknown value
8
Exact correspondence on both sides
9
Steepness of a line
10
Number divisible only by 1 and itself
13
U-shaped curve of a quadratic function