Chapter 9, Lesson 12


9-12.A understand the meaning of regular with respect to polygons
Which statement is not always true?
I
If a triangle has three congruent sides, it also has three congruent angles. So an equilateral triangle is a regular polygon.
II If a quadrilateral has four congruent sides, it also has four congruent angles. So an equilateral quadrilateral is a regular polygon.
III If a pentagon has five congruent sides, it also has five congruent angles. So an equilateral pentagon is a regular polygon.
(a) I and II only (b) I and III only (c) II and III only (d) III only

9-12.B find the sum of the measures of the interior angles of any polygon
What is the sum of the measures of the interior angles of any 12-gon?

9-12.C find the measure of an interior angle of a regular polygon
What is the measure, to the nearest degree, of an interior angle of any regular 14-gon?