Goal:Angle pairs are imperative to geometry. This lesson introduces students to common angle pairs.
Inquiry Learning!Students should be encouraged to learn through self-discovery whenever possible. To illustrate
the concept of the Linear Pair Postulate, offer several examples of linear pairs. Have students measure each angle
and find the sum of the linear pair. Students should discover any linear pair of angles is supplementary.
To further illustrate the idea of vertical angles, extend the adjacent ray of the previous linear pairs to a line. Have
students repeat the process of measuring the angles, notating the linear pairs. Students will come to the conclusion
that the angles opposite in the[U+0080][U+009C]X[U+0080][U+009D]are equal.
Students tend to get confused with the termvertical,as in vertical angles. Vertical angles are named because the
angles share a vertex, not necessarily because they are in a vertical manner.
Interdisciplinary Connection!NASA has developed many lesson plans that infuse science, technology, and mathe-
matics. The following link will take you to a lesson plan incorporating the seasons and vertical angles. http://sunea
rthday.nasa.gov/2005/educators/AOTK_lessons.pdf
Classifying Triangles
Pacing:This lesson should take one class period
Goal: Students have previously experienced triangle terminology: scalene, equilateral, isosceles. This lesson
incorporates these terms with other defining characteristics.
In Class Activity:Give pairs of students three raw pieces of spaghetti (you can also use non-bendy straws). Instruct
one partner to recreate the below table while the second makes two breaks in the spaghetti. It is okay if some breaks
away!
The students are to measure the three pieces formed by the two breaks and attempt to construct a triangle using these
segments. Students will reach the conclusion that the sum of two segments must always be larger than the third
if a triangle is to be formed.The Triangle Inequality Theorem can be found in the lesson entitled Inequalities in
Triangles
TABLE1.2:
Segment 1 Length (in cm) Segment 2 Length (in cm) Segment 3 Length (in cm) Can a triangle be formed
(Yes/No)Showing students the difference between line segments and curves, introduce cooked spaghetti. The flexibility of
the spaghetti demonstrates to students that segments must be straight in order to provide rigidity and follow the
definitions of polygons.
Students can express the concepts presented in this lesson using a Venn diagram or a hierarchy. If students are not
familiar with a hierarchy, remind students a hierarchy is an ordering of related objects from the most general to the
most specific. An example is shown below.
Chapter 1. Geometry TE - Teaching Tips