Problem:
A figure is an equiangular parallelogram if and only if it is a
Answer Choices:
A. rectangle
B. regular polygon
C. rhombus
D. square
E. trapezoid
Solution:
A parallelogram has (among other things) angles. "Equiangular" means that all angles are equal, so they are all . Thus all equiangular parallelograms are rectangles. (They are not all squares since adjacent sides of a parallelogram need not be equal.) Conversely, every rectangle is a -sided, equiangular figure with opposite sides parallel. Thus a figure is an equiangular parallelogram if and only if it is a rectangle.