Lesson Twentieth Review
Name all the triangles. (Diagram 16.)
Why is Fig. A a triangle?
What is a triangle?
What other name is sometimes given to triangles?
Name all the quadrilaterals.
Why is Fig. B a quadrilateral?
What is a quadrilateral, or quadrangle?
Name all the pentagons, hexagons, heptagons, octagons, and nonagons.
Why is C a pentagon? What is a pentagon? A hexagon? A heptagon? &c.
How many polygons in the diagram?
What is a polygon?
If each side of Fig. B is one inch, how many inches are there in its perimeter?
When is a polygon regular?
Name all the regular polygons in diagram 16.
Name all the irregular polygons.