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Recap: Area of a Circle

Part of the Circles section of Coddy's Geometry journey. Lesson 12 of 59.

Challenge

The area of circle O is 100π. Find its circumference C, exact in terms of π, then press Check.

Try it yourself

$Find the marked part of the figure$

Find the marked part of the figure

All lessons in Circles

1Parts of a Circle

Center and Radius Chords and Diameters Recap: Parts of a Circle

4Arcs and Sectors

Arc Length Area of a Sector Find the Central Angle The Missing Central Angle Recap: Arcs and Sectors

7Angles in a Semicircle

Thales' Theorem The Right Angle Inside Is That Enough?Semicircle With Letters Recap: Semicircles

10Tangents

What a Tangent Is Tangent and Radius Tangent Lengths Two Tangents From a Point Tangents With Letters Recap: Tangents

2Circumference

The Hexagon Inside Around the Circle Radius From Circumference Recap: Circumference

5Radii Make Isosceles

Two Radii, One Triangle Base Angles From the Center The Angle at the Center Isosceles With Letters Recap: Radii and Triangles

8Angles on the Same Arc

Same Arc, Same Angle Using the Same Arc Spot the Bow Tie Same Arc With Letters Recap: Same Arc

11Circle Chases

Tangent Meets Chord Two Roads to One Angle Enough to Find It?Cyclic Meets Isosceles Recap: Circle Chases

3Area of a Circle

The Area Formula Area From the Diameter Radius From the Area Circumference to AreaRecap: Area of a Circle

6Inscribed Angles

Meet the Inscribed Angle Half the Central Angle Twice the Inscribed Angle The Big Arc Inscribed With Letters Recap: Inscribed Angles

9Cyclic Quadrilaterals

Four Corners on a Circle Opposite Angles Add to 180 Is It Cyclic?Cyclic With Letters Recap: Cyclic Quadrilaterals

12Final Challenges

Final: The Pizza Slice Final: Paths to the Pond Final: The Curved Track Final: Deep in the Circle Final: Angle Into Arc