Download Section 8.5 Trapezoids

Geometry – Chapter 8 Lesson Plans
Section 8.5 – Trapezoids
Enduring Understandings: The student shall be able to:
1. identify and use the properties of trapezoids and isosceles trapezoids
Standards:
11. Points, Lines and Planes
Classifies triangles as acute, right, obtuse, equilateral, isosceles, scalene; and
classifies polygons as regular, convex, congruent.
14. Points, Lines and Planes
States and applies the triangle sum, exterior angles, and polygon angle sum theorems.
19. Congruence
States and applies properties of triangles and quadrilaterals such as parallelograms,
rectangles, rhombi, squares, and trapezoids.
21. Similarity
Uses properties of quadrilaterals to establish and test relationships involving
diagonals, angles, and lines of symmetry.
Essential Questions: What is a trapezoid? How does it fit in with the other
quadrilaterals?
Warm up/Opener:
Activities: Lesson/Body:
Definitions: - Make a drawing as I describe the vocabulary.
A Trapezoid is a quadrilateral with exactly on pair of parallel sides. The parallel sides
are called bases (so it has two bases). The non-parallel sides are called legs. Each
trapezoid has two pairs of base angles.
Read Example 1.
The median of a trapezoid is the segment that joins the midpoints of its legs.
Thm 8-13: (give without proof) The median of a trapezoid is parallel to the bases, and
the length of the median equals one-half the sum of the lengths of the bases.
If the legs of a trapezoid are congruent, the trapezoid is an isosceles trapezoid. Like the
base angles of an isosceles triangle being equal:
Thm. 8-14: Each pair of base angles in an isosceles trapezoid is congruent.
Do problems 23-28
Do the Venn diagrams for the quadrilaterals we have studied in this chapter. The
trapezoid has no shared characteristics with the parallelogram except that they are all
quadrilaterals.
Assessments:
CW WS 8.5
HW pg 337-338, # 9 - 35 odd (9)