A circle can be named by its center using the symbol. A circle with a center labeled C would be named C. An unbroken part of a circle is called an arc. 2 Types of arcs: 1.A minor arc of a circle is an arc that is shorter than half the circle and named by its endpoints. Circles 2.A major arc of a circle is an arc that is longer than half the circle and named by its endpoints and one other point on the arc.
P A B C Central Angle : An Angle whose vertex is at the center of the circle Minor ArcMajor Arc Less than 180° More than 180° AB ACB To name: use 2 letters To name: use 3 letters APB is a Central Angle
P E F D Semicircle: An Arc that equals 180° EDF To name: use 3 letters
THINGS TO KNOW AND REMEMBER ALWAYS A circle has 360 degrees A semicircle has 180 degrees Vertical Angles are Equal A C BD
measure of an arc = measure of central angle A B C Q 96 m AB m ACB m AE E = = = 96° 264° 84° EQA is a central angle. EQA is ??°
Arc Addition Postulate A B C m ABC = m AB + m BC Arc Addition Postulate: The measure of an arc formed by two adjacent arcs is the sum of the measures of the two arcs.
Tell me the measure of the following arcs. 80 100 40 140 A B C D R m DAB = m BCA = 240 260
Identify congruent arcs Congruent circles are 2 circles with the same radius. Congruent arcs are 2 arcs with the same measure that are arcs of the same circle or of congruent circles.
RQ P 6 P Q R 12