Radius and Tangent – Proof

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.

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CCSS: Adaptable
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

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

  • None
Common Core