A tangent line always finds its place at a 90-degree angle to a radius. Many scholars struggle with the proof of the seemingly simple statement. A brief video demonstrates the reasoning behind the proof before pupils practice applying it on their own.

Concepts

circles, radius, tangent lines

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Additional Tags

math

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Instructional Ideas

• Have pupils write the reasoning for each of the steps presented in the proof
• Go into detail on why geometry uses some letters more often than others
  

Classroom Considerations

• Relies on prior knowledge of circles, radius, tangent, perpendicular lines, and angles

Pros

• Includes both textbook practice problems as well as a worksheet
• Works well in traditional or flipped classes

Cons

• None

Common Core

HSG-C.A.4