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All you need to know about Circles! By: Ms. Erwin
Circle Book Notes! All you need to know about Circles! By: Ms. Erwin
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Day 1
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Tangent Chord VOCAB Inscribed Angle Central Angle Secant
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Major Arc Minor Arc A Minor Arc = π΄π΅ Major Arc = π΄πΆπ΅
A Minor Arc is named by two endpoints, and it measures between 0Β°<π<180Β° A Major Arc is named by Three points on the arc, and it Measures between π>180Β° Major Arc B E C Semicircle= π΅π·πΆ We name a circle based on its βCenterβ E is the Center We would call this circle, βCircle Eβ A circle measures exactly π=360Β° A Semicircle is named by Three points on the arc, and it Measures exactly π=180Β° D
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Inscribed Quadrilateral Inscribed Quadrilateral:
F F π¬πΏ π: VOCAB: <πΆπΉπ· is an INSCRIBED ANGLE <πͺππ«= π π π π©πͺ Inscribed Quadrilateral A B C D B C E πππΆπ΄π΅: <πΆπΈπ· is a CENTRAL ANGLE <πͺπ¬π«=π π«πͺ Inscribed Quadrilateral: Opposite Angles are SUPPLEMENTARY! Central Angle π¬πΏ π: D
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ππ π: ππΒ°= π πͺπ« If <πͺππ«=ππΒ°, ππππ
π πͺπ« <πͺππ«= π π π πͺπ«
C D F If <πͺππ«=ππΒ°, ππππ
π πͺπ« ππΒ° <πͺππ«= π π π πͺπ« ππ= π π π πͺπ« ππΒ°= π πͺπ«
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EX 2: If Opposite angles are supplementary in an inscribed quadrilateral, find the following measure. <π·=71Β° Find the measure of <π΅ A B C D <D+<B=180 71+<B=180 <B=109Β°
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Day 2
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Angle Relationships Angles formed by one Angles formed by CHORDS:
SECANT and one TANGENT: Angles formed by CHORDS: <π΄πΈπ΅ B A C D A B C D E <π΄πΈπ΅= π΄π΅ + π·πΆ 2 <π΄π΅πΆ= π΄π·π΅ 2 Angles formed by two SECANTS: Ex 3: Ex 4: Ex 5: Angle Relationships A C B F G <π΄π΅πΆ <π΄π΅πΆ= π΄πΆ β πΉπΊ 2
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Find the π<π·πΈπ΄ if π π·π΄ =104Β°, π π·πΆ =76Β°, πππ π π΄π΅ =65Β°,
Ex 3: Ex 5: B A C D A B C D E 156Β° 65Β° π π΅πΆ =360Β°β 104Β°+65Β°+76Β° 104Β° π π΅πΆ =115Β° <π·πΈπ΄= π·π΄ + π΅πΆ 2 π π΅π·π΄ =360Β°β156Β° 76Β° <π·πΈπ΄= 104Β°+115Β° 2 π π΅π·π΄ =204Β° <π·πΈπ΄=109.5Β° <πΆπ΅π΄= π΅π·π΄ 2 <πΆπ΅π΄= 204Β° 2 Ex 4: Find the π<π΄π΅πΆ if π π΄πΉ =70Β°, π πΊπΆ =143Β°, πππ π π΄πΆ =98Β°, 70Β° A C B F G π πΉπΊ =360Β°β 70Β°+98Β°+143Β° <πΆπ΅π΄=102Β° π π΅πΆ =49Β° 98Β° <π΄π΅πΆ= π΄πΆ β πΉπΊ 2 143Β° <π΄π΅πΆ= 98Β°β49Β° 2 <π΄π΅πΆ=24.5Β°
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Day 3-4
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Segment Relationships
One Secant and one Tangent Intersect! Two Chords Intersect! A B C D E B A C D π΄πΈ β πΈπΆ = π·πΈ β πΈπ΅ π΄π· β π΅π· = ( πΆπ· ) 2 Segment Relationships Two Secants Intersect! EX 6: EX 7: EX 8: A C B F G π΄π΅ β πΉπ΅ = πΆπ΅ β πΊπ΅
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EX 6: Find π΄πΈ if πΈπ΅ =8, π·πΈ =6, and πΈπΆ =12
C B F G A B C D E π΄πΈ β πΈπΆ = π·πΈ β πΈπ΅ π΄πΈ β12=6β8 π΄πΈ β12=48 EX 8: Find π΄π΅ if πΆπ΅ =10, πΊπ΅ =5, and πΉπ΅ =4 π΄πΈ =4 π΄π΅ β πΉπ΅ = πΆπ΅ β πΊπ΅ EX 7: Find πΆπ· if π΄π΅ =5, π΅π· =4 π΄π΅ β4=10β5 π΄π· β π΅π· = ( πΆπ· ) 2 B A C D π΄π΅ β4=50 9β4= ( πΆπ· ) 2 π΄π΅ =12.5 36= ( πΆπ· ) 2 6= πΆπ·
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If two chords are congruent, then the arcs are congruent
B C If two chords are congruent, then the arcs are congruent ππ π΄π΅ β
πΆπ΅ π‘βππ π΄π΅ β
πΆπ΅ A C B D E If a radius or diameter is perpendicular to a chord, then the radius bisects the chord, and the arc. ππ π΄π· ππ πππππππππ’πππ π‘π π΅πΆ π‘βππ π΅π· β
πΆπ· and π΅πΈ β
πΈπΆ A C B D E F G H I Two chords are congruent, if and only if they are equidistant from the center. πΊπ» β
π΅πΆ ππ πππ ππππ¦ ππ π΄πΈ β
π΄πΈ
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A line is tangent to a circle if and only if
it is perpendicular to a radius drawn at the point of tangency πΆπ΄ ππ π‘ππππππ‘ π‘π ππππππ π. π΄ ππ π‘βπ πππππ‘ ππ π‘πππππππ¦ A C T Z X Y If two segments from the same exterior point are tangent to a circle, then they are congruent ππ πππ ππ πππ π‘ππππππ‘ π‘π π‘βπ ππππππ. πβπ’π . ππ β
ππ
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Day 5
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Arc Length Sector Area A piece of the circumference of a circle
A slice of the circle bounded by 2 radii and an arc π΄ππ πΏππππ‘β= π₯Β° 360Β° β2ππ ππππ‘ππ π΄πππ= π₯Β° 360Β° βπ π 2 Ex 9: Find the length of arc πΈπΉ in circle S if ES=6 Ex 10: Find the area of the blue sector in Cricle M if AM=5 and π΄π
=150Β° E F S A R M
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Ex 9: πΉπππ π‘βπ πππππ‘β ππ πππ πΈπΉ
ππ ππππππ π ππ πΈπ=6ππ, πππ π<πΈππΉ=60Β° π΄ππ πΏππππ‘β= π₯Β° 360Β° β2ππ E F S πΈπΉ = 60Β° 360Β° β2πβ6 πΈπΉ =6.3 ππ Ex 10: Find the area of the blue sector in Cricle M if AM=5cm and π΄π
=150Β° ππππ‘ππ π΄πππ= π₯Β° 360Β° βπ π 2 A R M ππππ‘ππ π΄πππ= 150Β° 360Β° βπ 5 2 ππππ‘ππ π΄πππ=32.7 ππ 2
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Day 6
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Radian Measure We indicate radian measure using the symbol for a central angle π½ π»ππ πππππ ππππππ π»ππππ Radian measure is the ratio of the arc length, l, to the radius of the circle π½= π π πππΒ°=ππ
πππ
ππππ
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So if πππΒ°=ππ
πππ
ππππ, then what would πππΒ°ππ ππ πππ
ππππ?
πππΒ°=π
πππ
ππππ Lets see if we can come up with more radian measures π
π π
π 90Β°= ___________πππππππ π
ππ
ππ
π 270Β°= ___________πππππππ ππ
π
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Ex 1:
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You Try!
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You Try!
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Equation of a Circle βCenter-Radius Formβ
Any circle can be expressed in the standard form (π₯ββ) 2 + (π¦βπ) 2 = π 2 Where the center of the circle is at the point β,π And the radius of the circle is π
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EX: 1 Write the equation of the circle with a center at (3, β3) and a radius of 6. (x β h)2 + (y β k)2 = r 2 Equation of circle (x β 3)2 + (y β (β3))2 = 62 Substitution (x β 3)2 + (y + 3)2 = 36 Simplify. (x β 3)2 + (y + 3)2 = 36
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You Try! Write the equation of the circle with a center at (2, β4) and a radius of 4. A. (x β 2)2 + (y + 4)2 = 4 B. (x + 2)2 + (y β 4)2 = 4 C. (x β 2)2 + (y + 4)2 = 16 D. (x + 2)2 + (y β 4)2 = 16
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You Try Again! Write the equation of the circle graphed to the right.
A. x2 + (y + 3)2 = 3 B. x2 + (y β 3)2 = 3 C. x2 + (y + 3)2 = 9 D. x2 + (y β 3)2 = 9
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You Try! Which of the following is the graph of x2 + y2 β10y = 0?
A. B. C. D.
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