Circles, Arcs & Sectors

The radius controls a circle's metric structure; circumference and area scale differently, while arcs and sectors represent fractions determined by central angle.

What you'll learn

  • Distinguish radius from diameter.
  • Interpret circumference as boundary length and area as square-unit coverage.
  • Explain why doubling radius doubles circumference but quadruples area.
  • Find arc and sector fractions from central angles.
  • Subtract concentric circle areas and coordinate circle geometry with right triangles.

Before you start

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