1. GEOMETRY PRE-AP CIRCLES VOCABULARY

2. You can’t do the easy math if you don’t do the memory work!
You need to know ALL of this vocabulary to do your investigations on circles!
Fill in the blanks below, and memorize these definitions!
Also use the circle provided to draw a diagram if not already illustrated.
The math is easy in this chapter, but there is lots of memory work!
You can’t do the easy math if you don’t do the memory work!

3. Holt Geometry, Texas Edition
All information is taken from the green Holt Geometry book, Texas Edition, on the bookshelf by computer #1 in my room.

4. 1. Page 600 and 746:
A circle is the set of all points in a plane that are equidistant from a given point, called the center of the circle.

5. 2. Page 746:
A chord of a circle is a segment whose endpoints lie on the circle.

6. 3. Previous knowledge and page 37:
A diameter of a circle is a chord that passes through the center.

7. 4. Previous knowledge and page 37:
A radius of a circle is a segment that has the center as one endpoint and a point on the circle as the other endpoint.

8. 5. Previous knowledge:
The diameter is twice the length of the radius.

9. 6. Page 746: A line is tangent to a circle
if it intersects the circle at
exactly one point.
If it intersects at two points,
then the line is a secant of
the circle.

10. 7. Page 746:
The point at which a line intersects the circle at exactly one point is called the point of tangency.

11. 8. Page 747:
Two circles are congruent circles if and only if they have congruent radii.

12. 9. Page 747:
Concentric circles are coplanar circles with the same center.

13. 10. Page 747:
Two coplanar circles that intersect at exactly one point are called tangent circles.
They can be internally tangent circles (left diagram) or externally tangent circles (right diagram).

14. 11. Page 748:
A common tangent is a line that is tangent to two circles.
The left diagram shows two circles that are externally tangent; the right diagram shows two circles that are internally tangent.

15. 12. Previous knowledge, page 309:
A circle is inscribed in a polygon if each side of the polygon is tangent to the circle.

16. 13. Previous knowledge, page 308:
A circle is circumscribed about a polygon if each vertex of the polygon lies on the circle.

17. 14. Page 756:
An angle whose vertex is the center of a circle is a central angle of the circle.

18. 15. Page 756:
If the measure of an arc is less than 180°, then the arc is a minor arc.
AB or BA
Note: Sketchpad will
always name an arc
counterclockwise.

19. 16. Page 756:
If the measure of an arc is more than 180°, then the arc is a major arc.
CDE or EDC
Note: Sketchpad will
always name an arc
counterclockwise.

20. 17. Page 756:
If the endpoints of an arc are the endpoints of a diameter, then the arc is a semicircle and its measure is 180°.
FGH or HGF
Note: Sketchpad will
always name an arc
counterclockwise.

21. 18. Page 757:
Adjacent arcs are arcs of the same circle that intersect at exactly one point.
LK and KJ are adjacent arcs
Note: Sketchpad will
always name an arc
counterclockwise.

22. 19. Page 764:
A sector of a circle is a region bounded by two radii of the circle and their intercepted arc.
Sector MON or Sector NOM.

23. 20. Page 765:
A segment of a circle is a region bounded by an arc and its chord.
Segment POQ or
Segment QOP.

24. 21. Page 772:
An angle is an inscribed angle if its vertex is on the circle, and the two sides of the angle are chords.

25. 22. Page 772:
An intercepted arc consists of endpoints that lie on the sides of an inscribed angle and all the points of the circle between them.
RS or SR