Geometry Lesson
Circles: From Central Angles to Secants, Tangents & Sector Area
Shared by A STEM Educator
High SchoolBTC Style / Thinking ClassroomsCCSS.MATH.CONTENT.HSG.C.A.2,CCSS.MATH.CONTENT.HSG.C.A.3,CCSS.MATH.CONTENT.HSG.C.B.550 min
Learning Objective
Students will determine arc measures, central and inscribed angle measures, angles formed by chords/secants/tangents, and sector areas using circle theorems.
Lesson Overview
Students progress from identifying central and inscribed angles through arc measures, then tackle chord, secant, and tangent angle relationships, culminating in sector area. Each task changes exactly one variable to build confident mastery.
Materials
- Vertical whiteboards or chart paper
- Dry-erase markers
- Colored markers for arc highlighting
- Rulers/compasses (optional)
- Random grouping tool
Scaffolded Task Progression
1Task 1
In circle below, central angle . What is the measure of arc ?
[ Interactive graph / diagram, available in the full lesson ]
[ Interactive graph / diagram, available in the full lesson ]
2Task 2
In circle , central angle . Inscribed angle intercepts the same arc , where is a point on the major arc. What is ?
[ Interactive graph / diagram, available in the full lesson ]
[ Interactive graph / diagram, available in the full lesson ]
Unlock the full lesson
See all 7 scaffolded tasks, the full answer key, warm-up, exit slip, and a print-ready version — free to start.
Create a free accountAlready have an account? Sign in
Make it your own
Like this lesson but want to tweak it?
Make an editable copy and adjust the tasks, warm-up, and answer key to fit your class — no need to start from scratch.