Download Circle Book Notes!

Day 1
Tangent
Chord
Inscribed Angle
Central Angle
Secant
• Chord: A segment with endpoints that are on the
circle
• Tangent: A line that intersects the circle in exactly
one point (touches, but does not cross through)
• Inscribed Angle: An angle that has a vertex on a
circle and sides that contain chords of the circle
• Central Angle: An angle that intersects a circle in
two points and has its vertex at the center of the
circle
• Secant: Any line that intersects a circle in exactly
two points
A
Minor Arc = 𝐴𝐵
Major Arc = 𝐴𝐶𝐵
Named by
two endpoints
Measures
between 0° < 𝜃 < 180°
Named by
Three points (two endpoints
with one in between)
Measures 𝜃 > 180°
B
E
C
Circle = ⊙E
Semicircle = 𝐵𝐷𝐶
Named by its “Center”
“Circle E”
Measures exactly
𝜃 = 360°
Named by
Three points (two endpoints
with one in between)
Measures exactly
𝜃 = 180°
D
A
F
𝑬𝑿 𝟏:
A
B
D
VOCAB:
< 𝐶𝐹𝐷 is an INSCRIBED ANGLE
B
𝟏
< 𝑪𝑭𝑫 = 𝒎𝑪𝑫
𝟐
E
𝑉𝑂𝐶𝐴𝐵:
< 𝐶𝐸𝐷 is a CENTRAL ANGLE
< 𝑪𝑬𝑫 = 𝒎𝑫𝑪
𝑬𝑿 𝟐:
C
Inscribed Quadrilateral:
Opposite Angles are
SUPPLEMENTARY!
D
C
𝐄𝐗 𝟏:
If < 𝑪𝑭𝑫 = 𝟒𝟓°, 𝒇𝒊𝒏𝒅 𝒎𝑪𝑫
F
𝟒𝟓°
𝟏
< 𝑪𝑭𝑫 = 𝒎𝑪𝑫
𝟐
𝟏
𝟒𝟓 = 𝒎𝑪𝑫
𝟐
𝟗𝟎° = 𝒎𝑪𝑫
C
D
EX 2:
If Opposite angles are
supplementary in an inscribed
quadrilateral, find the following
measure.
A
B
D
< 𝐷 = 71°
Find the measure of < 𝐵
< D +< B = 180
C
71 +< B = 180
< B = 109°