Properties of Circles - Grade 6
Unit Circle
A circle at the origin (0, 0) and has a radius of one centered on the coordinate plane system
Tangent Line
A line in the plane of a circle that intersects the circle in exactly one point.
chord
A line segment with both endpoints on the circle. Always shorter than the diameter.
secant
A line that intersects a circle at exactly two points.
sector
A part of a circle enclosed by tow radii and an arch connecting them
arc length
A portion of the circumference of a circle named and measured by its endpoints
radius
A straight line from the center to the edge of a circle or sphere. The radius is half the diameter.
diameter
A straight line passing from side to side through the center of a circle or sphere. The diameter is twice the radius.
central angle
An angle formed by two radii of a circle and whose vertex is the center of the circle.
inscribed angle
An angle whose vertex is on a circle and whose sides contain chords of the circle.
reflex angle
Between 180 and 360 degrees.
Tangent Circles
Circles (also known as kissing circles) are circles in a common plane that intersect in a single point.
semi circle
Half of a circle.
circle
Is the set of points which are all the same distance (its radius) from the center.
center
Mid-point of a circle.
pi (π)
The Greek letter used to represent the ratio of the circumference to the diameter of a circle.
36
The central angle measure is _______ degrees when the sector of a circle makes up 10% of the circle. (10% of 360 degrees)
108
The central angle measure is _______ degrees when the sector of a circle makes up 30% of the circle. (30% of 360 degrees)
252
The central angle measure is _______ degrees when the sector of a circle makes up 70% of the circle. (70% of 360 degrees)
vertex
The common endpoint of an angle.
circumference
The distance around a circle. C = πd
360
The number of degrees in a circle
90
The the central angle measure is _______ degrees when the sector of a circle makes up 25% of the circle? (25% of 360 degrees)
180
What is the central angle measure is _______ degrees when the sector of a circle makes up 50% of the circle. (50% of 360 degrees) in this circle it would be section "A".