23+Basic+Circle+Vocab,+Central+and+Inscribed+Angles

=**Intro to Circles** = Basic Circle Vocabulary consists of words that you need to know before you even begin to start to do any actual math or equations when dealing with circles. Central Angles are angles that have a vertex that lies on the center of a circle. We go into more depth of what that mean below. Inscribed Angles are angles where the vertex of the angle lies on any point on the circle. We also go more in depth on that as well. This page is a basis of what you need to know before you start really working with circles. //Basic Circle Vocabulary // 1. **Arc:** An unknown part of a circle…any two points on a circle are the endpoints of the arc between them. Like an angle, arc’s have a corresponding degree measure 2. **Minor Arc:** An arc measuring less than 180 degrees. Minor arcs are named using the arc’s endpoints with an arched “hat”. The measure of a minor arc is equal to the measure of its ventral angle 3. **Major arc:** An arc measuring more than 180 degrees, but less than 360 degrees. Major arcs are named for the endpoints and a point between then. The measure of a major arc is equal to 360 degrees minus the measure of its minor arc 4. **Semicircle:** An arc whose endpoints are on a diameter of the circle. A semicircle also uses three-letter notation. A semicircle measures 180 degrees 5. **Adjacent Arc:** Two arcs in the same circle with exactly one point in common (an endpoint) 6. **Intercepted Arc:** The arc formed by intersecting an angle with a circle (the arc: cutoff: by an angle) 7. **Tangent:** A line in the plane of a circle that intersects the circle in exactly one point. The point where the line and circle intersect is called the point of tangency 8. **Secant:** A line in the plane of a circle that intersects the circle in exactly two points.These intersection points and the points between the form chords of the circle 9. **Radius:** a segment joining the center to a point on the circle. All radii are congruent 10. **Chord:** Any segment whose endpoints lie on a circle 11. **Diameter:** The longest chord in a circle → it passes through the center. D=2r 12. **Concentric Circle:** Circles that share the same center

//Central Angles

A central angle is an angle whose vertex is the center of a circle, and whose sides pass through a pair of points on the circle//



**//__Inscribed Angle:__//** An inscribed angle is when two secants intersect at a point on a circle.



Helpful Links 1. http://mathworld.wolfram.com/CentralAngle.html - For Central Angles 2. http://www.mathgoodies.com/lessons/vol2/geometry.html - For Terms 3. http://www.mathwarehouse.com/geometry/circle/inscribed-angle.html inscribed angles