1. Bell Ringer

2. The Language of Geometry: Sketching, Drawing, Naming, and Sorting Basic Geometric Figures
Chapter 13.1

3. When you sketch a geometric figure, the figure is created without the use of tools.
When you draw a geometric figure, the figure is created with the use of tools such as a ruler, a straightedge, a compass, or a protractor. A drawing is generally more accurate than a sketch.
When you construct a geometric figure, the figure is created using only a compass and a straightedge.

4. Triangles
A triangle is the simplest closed three-sided geometric figure.
How many line segments, angles, and vertices are needed to form a triangle?
To form a triangle, three line segments, three angles, and three vertices are needed.

6. Triangles are classified by their side lengths or by their angle measures.
The root word “equi” means “equal,” and the root word “lateral” means “side.”
An equilateral triangle is a triangle with all sides congruent.

7. An isosceles triangle is a triangle with at least two congruent sides.

8. A scalene triangle is a triangle with no congruent sides.

9. An acute triangle is a triangle that has three angles that each measure less than 90°.

10. A right triangle is a triangle that has a right angle.

11. An obtuse triangle is a triangle that has an angle measuring greater than 90°.

12. Quadrilaterals
A quadrilateral is a closed four-sided geometric figure.
Opposite sides are sides that do not share a common endpoint.
Consecutive sides are sides that share a common endpoint.

13. Examples

14. A quadrilateral is named using four capital letters representing the vertices, listed in a clockwise or counterclockwise order. The quadrilateral shown could be named quadrilateral ABCD, quadrilateral ADCB, quadrilateral BCDA, and so on.

15. Side AD is opposite side BC. Side AB is opposite side DC.
Name the two pairs of opposite sides of quadrilateral ABCD.
Side AD is opposite side BC.
Side AB is opposite side DC.

16. Side AB is consecutive to side BC. Side BC is consecutive to side CD.
Name the four pairs of consecutive sides of quadrilateral ABCD.
Side AB is consecutive to side BC.
Side BC is consecutive to side CD.
Side CD is consecutive to side DA.
Side DA is consecutive to side AB.

17. A Square
A square is a quadrilateral with all sides congruent and all angles congruent.

18. A Rectangle
A rectangle is a quadrilateral with opposite sides congruent and all angles congruent.

19. A Rhombus
A rhombus is a quadrilateral with all sides congruent. The plural of rhombus is rhombi.

20. A parallelogram
A parallelogram is a quadrilateral with both pairs of opposite sides parallel.

21. A Kite
A kite is a quadrilateral with two pairs of consecutive congruent sides with opposite sides that are not congruent.

22. A trapezoid
A trapezoid is a quadrilateral with exactly one pair of parallel sides.

23. An isosceles trapezoid
An isosceles trapezoid is a trapezoid whose non-parallel sides are congruent.

24. Polygons
Triangles and quadrilaterals are examples of geometric figures with many sides.
The root word “poly” means “many” and the root word “gon” means “side.”
A polygon is a closed figure that is formed by joining three or more line segments at their endpoints.

25. Polygons
A regular polygon is a polygon with all sides congruent and all angles congruent.
An irregular polygon is a polygon that is not regular.
Polygons are named using capital letters representing the vertices, listed in a clockwise or counterclockwise order.

26. A Pentagon
A pentagon is a five-sided polygon.

27. A Hexagon
A hexagon is a six-sided polygon.

28. A Heptagon
A heptagon is a seven-sided polygon.

29. An Octagon
An octagon is an eight-sided polygon.

30. A Nonagon
A nonagon is a nine-sided polygon.

31. A Decagon
A decagon is a ten-sided polygon.