Stage Five: Angles, Angles, and More Angles! (Vertical, Supplementary, Complementary)

Geometry Review

When we discuss geometry, angles are going to be a popular topic. It is necessary for students to have a firm grasp on the topic because it appears in geometry so often. Before continuing with the next stage of angles and geometry topics, teachers should quiz students on what they already know. In my own classroom I like to group students together and assign each group certain questions. This is a quick way to get an idea of who is grasping the subject or not.

Some examples of questions I asked were:

• What are the fundamental building blocks of geometry?
• What does a line segment look like?
• What do angle measurement problems consist of?
• Which is an obtuse angle? 130 degrees, 185 degrees, 90 degrees?
• What are three examples of a polygon?
• What are three examples of a polyhedron?

Vertical, Supplementary, and Complementary Angles

After quizzing and making sure my students understand these first few geometry stages, we take a look at the next stage of angles: vertical, supplementary, and complementary. Vertical angles are created by intersecting lines which are pairs of angles whose sides are two pairs of opposite rays. Supplementary angles are two angles whose sum of measure is 180 degrees. Complementary angles are two angles whose measure is 90 degrees.

Here is a trick I learned in one of my college classes to remember these angles. This helped me to remember them and can be quite useful when learning and teaching these angles. With supplementary angles, turn the S and U in supplementary into 80 and put a 1 in front of the word. For complementary angles, take the "C" and the "O" and turn it into 90. Vertical angles are congruent meaning they are exactly the same. Here's a chart I made of these tricks:

WEBSITE:
http://www.algebralab.org/lessons/lesson.aspx?file=geometry_anglescomplementarysupplementaryvertical.xml