# Circles

## Circle basics

Learn
Circles glossaryRadius, diameter, circumference & πProof: all circles are similar

## Arc measure

Learn
Intro to arc measureFinding arc measuresFinding arc measures with equations
Practice
Arc measureGet 3 of 4 questions to level up!
Arc measure with equationsGet 3 of 4 questions to level up!

## Arc length (from degrees)

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Arc length from subtended angleSubtended angle from arc lengthChallenge problems: Arc length 1Challenge problems: Arc length 2
Practice
Arc lengthGet 3 of 4 questions to level up!

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Practice
Radians & degreesGet 3 of 4 questions to level up!

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Arc length as fraction of circumferenceArc length from subtended angle: radiansChallenge problems: Arc length (radians) 1Challenge problems: Arc length (radians) 2
Practice
Radians & arc lengthGet 5 of 7 questions to level up!

## Sectors

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Area of a sector
Practice
Area of a sectorGet 3 of 4 questions to level up!

## Inscribed angles

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Inscribed anglesChallenge problems: Inscribed anglesInscribed angle theorem proofInscribed angle theorem proof
Practice
Inscribed anglesGet 3 of 4 questions to level up!

## Inscribed shapes problem solving

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Proof: Right triangles inscribed in circlesInscribed shapes: find diameterInscribed shapes: angle subtended by diameterInscribed shapes: find inscribed angleChallenge problems: Inscribed shapesInscribed quadrilaterals proofSolving inscribed quadrilateralsProof: radius is perpendicular to a chord it bisectsProof: perpendicular radius bisects chordArea of inscribed equilateral triangle
Practice
Inscribed shapesGet 3 of 4 questions to level up!
Inscribed quadrilateralsGet 4 of 5 questions to level up!

## Properties of tangents

Learn
Proof: Radius is perpendicular to tangent lineDetermining tangent lines: anglesDetermining tangent lines: lengthsProof: Segments tangent to circle from outside point are congruentTangents of circles problem (example 1)Tangents of circles problem (example 2)Tangents of circles problem (example 3)Challenge problems: radius & tangentChallenge problems: circumscribing shapes
Practice
Tangents of circles problemsGet 3 of 4 questions to level up!

## Standard equation of a circle

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Features of a circle from its standard equationGraphing a circle from its standard equationWriting standard equation of a circle
Practice
Features of a circle from its standard equationGet 3 of 4 questions to level up!
Graph a circle from its standard equationGet 3 of 4 questions to level up!
Write standard equation of a circleGet 3 of 4 questions to level up!

## Expanded equation of a circle

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Features of a circle from its expanded equationCircle equation review
Practice
Features of a circle from its expanded equationGet 3 of 4 questions to level up!
Graph a circle from its expanded equationGet 3 of 4 questions to level up!

## Constructing regular polygons inscribed in circles

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Geometric constructions: circle-inscribed squareGeometric constructions: circle-inscribed equilateral triangleGeometric constructions: circle-inscribed regular hexagon

## Constructing circumcircles & incircles

Learn
Geometric constructions: triangle-inscribing circleGeometric constructions: triangle-circumscribing circle

## Constructing a line tangent to a circle

Learn
Geometric constructions: circle tangentGeometric constructions: circle tangent (example 2)