Across
1
Line segment connecting two circle points
4
Proven mathematical statement
5
Three-sided polygon
8
The number representing nothing
10
Rectangular array of numbers
13
Steepness of a line
Down
2
Power to which a number is raised
3
Number with digits after a point
6
Repeated addition
7
Line touching circle at one point
9
Total distance around a shape
11
Mathematical rule or equation
12
Round shape with all points equidistant