Across
1
Math using letters for unknown values
4
Result of addition
6
The number representing nothing
7
Line touching circle at one point
10
Difference between highest and lowest values
13
Repeated addition
Down
2
Longest side of a right triangle
3
Closed shape with straight sides
5
Total distance around a shape
8
Part of a circle's circumference
9
Corner point of a polygon
11
Symbol representing unknown value
12
Part of a whole number