10.2 Notes- Finding Arc Measure
EQ: How do you find the measure of an
arc of a circle?
Demonstrated in writing in practice
problems in notes.
Central Angle:
• An angle whose vertex is the center of the
circle.
EQ: How do you find the measure of an arc of a circle?
Demonstrated in writing in practice problems in notes.
Minor Arc:
Part of a circle that measures less than 180°
Named by 2 endpoints
EQ: How do you find the measure of an arc of a circle?
Demonstrated in writing in practice problems in notes.
Major Arc:
Part of a circle that measures between 180° and
360°
Named by the endpoints and a point between
them.
EQ: How do you find the measure of an arc of a circle?
Demonstrated in writing in practice problems in notes.
Semicircle:
An arc with endpoints that are the endpoints of
a diameter of a circle.
The measure of a semicircle is 180°
EQ: How do you find the measure of an arc of a circle?
Demonstrated in writing in practice problems in notes.
A
Minor Arc 𝐴𝐵
B
C
Central Angle C
D
Major Arc 𝐴𝐷𝐵
EQ: How do you find the measure of an arc of a circle?
Demonstrated in writing in practice problems in notes.
• Measure of a Minor Arc= Measure of the
central angle.
• Measure of a Major Arc = 360 – measure of
minor arc.
EQ: How do you find the measure of an arc of a circle?
Demonstrated in writing in practice problems in notes.
110°
360° - 110°
=250°
180 °
EQ: How do you find the measure of an arc of a circle?
Demonstrated in writing in practice problems in notes.
Adjacent Arcs:
• Arcs in the same circle that have a common
endpoint.
EQ: How do you find the measure of an arc of a circle?
Demonstrated in writing in practice problems in notes.
Arc Addition Postulate
The measure of an
arc formed by two
adjacent arcs is the
sum of the two
arcs.
EQ: How do you find the measure of an arc of a circle?
Demonstrated in writing in practice problems in notes.
137°
223°
220°
299°
EQ: How do you find the measure of an arc of a circle?
Demonstrated in writing in practice problems in notes.
Minor 120°
Major 240°
Semicircle 180° Minor 160°
Minor 80°
Semicircle 180°
EQ: How do you find the measure of an arc of a circle?
Demonstrated in writing in practice problems in notes.
Congruent Circles:
Circles that have the same radius
EQ: How do you find the measure of an arc of a circle?
Demonstrated in writing in practice problems in notes.
Congruent Arcs
Arcs that have the same measure and are arcs of
the same circle or congruent circles.
EQ: How do you find the measure of an arc of a circle?
Demonstrated in writing in practice problems in notes.
Yes, the central
No, the arcs have the same
angles are the
measure since they have
Yes b/c they are in
same and the
the same circle and the same central angle, but
circles are
they are not congruent
the central angles
congruent (since
since they are in different
are the same.
the radii are the
circles that are not
EQ: How do you find
the measure of an arc ofsame).
a circle?
congruent.
Demonstrated in writing in practice problems in notes.
Homework: Page 661 #3-14
EQ: How do you find the measure of an arc of a circle?
Demonstrated in writing in practice problems in notes.