1. Which polygon or polygons are regular?
A regular polygon is a polygon that is equiangular (all angles are equal in measure) and equilateral (all sides have the same length).
Therefore your answer is:
A. equilateral triangle
C. square
2. Which polygon is always irregular?
traingle - NOT (equilateral triangle)
trapezoid - YES
square - NOT
hexagon - NOT (regular hexagon)
Okay so a couple of things to know to best solve this problem
1) all angles in a triangle add to 180
2) a straight line the angles above it equal 180 and the angles below it add to 180
3) vertical angles are equal (vertical angles are angles that make an X the opposite angles are called vertical angles)