Geometry

Circles flashcards

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How are the radius and diameter of a circle related?Circle Parts and Angle Measures
The radius goes from the center to the circle’s edge. A diameter crosses the center and is two radii long.
How is a central angle related to its intercepted arc?Circle Parts and Angle Measures
A central angle has the same measure as its intercepted arc.
What does the equation of a circle describe?Circle Parts and Angle Measures
All points exactly one radius away from the center: (x − h)² + (y − k)² = r².
What is the difference between a minor arc and a major arc?Arcs and Chords
A minor arc measures less than 180°. The major arc is the rest of the circle: 360° minus the minor arc.
In the same circle, what is true about congruent chords?Arcs and Chords
Congruent chords intercept congruent arcs.
In the same circle, what is true about chords that are equidistant from the center?Arcs and Chords
They are congruent.
What does the Inscribed Angle Theorem say?Inscribed Angles
An inscribed angle measures half of its intercepted arc.
What is true about inscribed angles that intercept the same arc?Inscribed Angles
They are congruent.
What is true about the opposite angles of a quadrilateral inscribed in a circle?Inscribed Angles
They are supplementary; they add to 180°.
How does a tangent line meet the radius drawn to the point of tangency?Tangents and Secants
At a right angle; the tangent is perpendicular to the radius.
What is true about two tangent segments drawn to a circle from the same outside point?Tangents and Secants
They are congruent.
How do you find the angle formed by two secants that meet outside a circle?Tangents and Secants
Take half the difference of the intercepted arcs: ½(far arc − near arc).
How do you find the length of an arc?Arc Length and Sector Area
(central angle ÷ 360°) × 2πr.
How do you find the area of a sector?Arc Length and Sector Area
(central angle ÷ 360°) × πr².
What fraction of a circle does a sector with central angle θ represent?Arc Length and Sector Area
θ ÷ 360°.