Launch a Lesson on Parts of Circles with a Thinking Task

When introducing parts of a circle, it can be tempting to jump straight into definitions and diagrams. But students learn best when they first connect new ideas to something they already know. A thinking task creates the space for exploration, reasoning, and discovery before you step in with formal instruction. Here’s how you can structure a lesson on parts of a circle using this approach.

Launch: Review of basic geometry terms
Start by putting students in small groups at vertical non-permanent surfaces. Give them a partially completed table with three columns: term, diagram, and notation. Helpful terms would be angle, line segment, line, and ray — familiar vocabulary from earlier geometry work that will be used in the parts of circles.

Some rows of the table are filled in, while others are blank. For example, a diagram might be given but not the term, or notation provided but no diagram. Students must work together and use their reasoning skills to complete the missing pieces.

This thinking task is not yet about circles, but it primes students to recognize how these basic building blocks can appear in different contexts. More importantly, it gives them practice using precise mathematical language and notation before introducing circle-specific vocabulary.

Part 2: Exploring the parts of a circle
Once students have refreshed their knowledge, introduce the new content: the parts of a circle. Provide clear definitions terms and instead of just telling students to copy these down, give them blank circles and ask them to draw each part themselves. For example, after reading the definition of a secant, they must sketch it and label it correctly. This pushes them to think carefully about placement and relationships, and when done at VNPS in groups, students can see and compare different interpretations in real time.

 
Part 3: Guided notes for consolidation
After the group exploration, provide a structured set of guided notes. The format mirrors the opening table: definition, diagram, and notation. This time, however, you provide the definitions and leave either the diagram or the notation blank. Some rows might include a diagram so students must add the notation, while others give the notation and require them to sketch the diagram. This mix reinforces independence while still giving support.

 
Part 4: Practice for mastery
To wrap up the lesson, offer varied practice that asks students to apply what they’ve learned:

• Identify the circle part when given a diagram with notation
• Draw the diagram when given notation
• Match terms to their definitions

These practice tasks provide the necessary repetition, but in different formats so the work feels meaningful rather than rote.

Why this approach works
This structure mirrors the flow of deep learning:

• Start with what students know
• Explore new concepts through discovery
• Consolidate with notes
• Reinforce with practice

The thinking task at the beginning sets the tone; students are reasoning, talking, and making connections from the very first minute. By the time they reach formal notes and practice, the vocabulary feels earned rather than imposed.

If you’d like a complete version of this lesson with the thinking task, guided notes, and practice pages you can grab it at the link below.  It’s designed for group work at VNPS or independent practice, and it includes all the diagrams and notation you need.

CLICK HERE TO GRAB THE RESOURCE