Angles, Circles, and parts of Circles

secant: a line, ray, or segment that contains a chord chord: segment has endpoints on circle tangent: a line, ray, or segment that touches the circle in one point

Tangent: a line, ray, or segment that only intersects the circle at one point AB is tangent to circle at point C

Central angle: vertex is at the center of the circle Vertex is C. Central Angle is named <ACB or <BCA CENTRAL ANGLE is ALWAYS in the CENTER of the CIRCLE!

Chord: segment whose endpoints lie on the circle AD is a chord. BD is a chord. Note that AC and CB are NOT chords because C is not on the circle.

Inscribed angle: vertex on the circle and sides contain chords of circle Inscribed Angle is named <ADB or <BDC. Know the difference between Inscribed angles and Central Angles.

Arc: an unbroken part of a circle minor arc: (use 2 letters) less than ½ the circle major arc: (use 3 letters) more than ½ the circle congruent arcs: arcs with same measure Arc Addition postulate The measure of the arc formed by 2 arcs that have exactly one point in common is the sum of the measures of the two arcs. AB + BC = AC

Tangent Theorem: Segment is tangent to a circle if and only if it is perpendicular to a radius of a circle at the point of intersection.

Practice Problems!!!! Name the following in the diagram A chord A secant An inscribed angle A central angle A line tangent to the circle A minor arc A major arc Click on next slide to see if your answers are correct.

Practice Problems!!!! Name the following in the diagram A chord DC or DA A secant line m An inscribed angle <ADC A central angle <ABD or <ABC A line tangent to the circle line h A minor arc AD or AC A major arc CDA or ADC