Across
1
U-shaped curve of a quadratic function
4
Collection of distinct elements
5
Exact correspondence on both sides
8
Line touching circle at one point
9
Line crossing from corner to corner
12
Three-sided polygon
Down
2
Math using letters for unknown values
3
Part of a circle's circumference
6
Symbol representing unknown value
7
The number representing nothing
10
Distance from center to edge of circle
11
Steepness of a line