Unit H Flashcards
Central Angle
An angle whose vertex is the center of the circle
Circle
The set of all points equidistant from a given point called the center
Arc
A part of a circle
Semicircle
Half of a circle
Minor Arc
Less than a semi circle
Major Arc
Greater than a semicircle
Adjacent Arcs
Arcs of the same circle with one point in common
Arc Addition Postulate
The measure of the arc formed by two adjacent arcs is the sum of the measures of the two arcs
Arc Length
A fraction of a circle’s circumference
Length of AB = (mAB)/360 x 2 pi r
Tangent
To a circle is a line in the plane of the circle that intersects the circle in exactly one point
Point of Tangency
The point at which the tangent and a circle intersect
Theorem 11-1
If a line is tangent to a circle, then it is perpendicular to the radius drawn to the point of tangency
Theorem 11-2
If a line in a plane of a circle is perpendicular to the radius at its endpoint on the circle, then the line is tangent to the circle
Inscribed in
When all 3 points of a triangle lie on a circle ( triangle is in circle )
Circumscribed in
When each side of a triangle is tangent to a circle ( triangle is outside of the circle )
Theorem 11-3
The two segments tangent to the circle from a point outside the circle are congruent
Chord
A segment whose endpoints are on a circle
Theorem 11-4
Congruent central angles have congruent chords
Congruent chords have congruent arcs
Congruent arcs have congruent central angles
Theorem 11-5
Chords equidistant from the center are congruent
Congruent chords are equidistant from the center
Theorem 11-6
In a circle, a diameter that is perpendicular to a chord, bisects the chord and its arc
Theorem 11-7
In a circle, a diameter that bisects a chord is perpendicular to the chord
Theorem 11-8
In a circle, the perpendicular bisector of a chord contains the center of the circle
