Arc Measures
I.SectionObjectives
- Measure central angles and arcs of circles.
- Find relationships between adjacent arcs.
- Find relationships between arcs and chords.
II.MultipleIntelligences
- Define Central angle
- Define arc
- In each part of this lesson, work with each diagram and then have the students brainstorm different observa-
tions about each diagram. Then give them the information from each diagram. - For example, begin with the diagram that demonstrates the Arc Addition Postulate. It is common sense that
the two arcs would add up to be the total. Give students the name of the postulate and ask them to come up
with the meaning of the postulate given the diagram. Then walk them through it. - Do the same with the diagram on the congruent chords.
- In Example 1- show that all angles must add to be 360◦.
- Use the straight line to show the 180◦, then talk to the students about working through the puzzle of figuring
out the measure of each angle inside the circle. - Keep this lesson interactive and engage students in participating in the discussion.
- Refrain from simply presenting the material to them.
- Intelligences- linguistic, logical- mathematical, visual- spatial, interpersonal
III.SpecialNeeds/Modifications
- Define semicircle with a diagram.
- Define major arc with a diagram- named with three letters.
- Define minor arc with a diagram- named with two letters (endpoints).
- Review solving multi- step equations.
- Present diagrams first and then engage the students in a discussion about the diagram.
IV.AlternativeAssessment
- Create a checklist of important points that you want students to discover in the lesson.
- Then listen for these points while you discuss the information and present the material to the students.
- During the practice exercises, pair students up to work together. This will help students to clarify the given
information.
Chords
I.SectionObjectives
- Find the lengths of chords in a circle.
- Find the measure of arcs in a circle.
II.MultipleIntelligences
4.9. Circles