SlideShare a Scribd company logo
(a) Proving Angle Properties of Circles
A B P O C that the angle subtended by an arc at the  centre  of a circle is  twice  that subtended at the  circumference  of the same circle .  ∠ AOB  = 2 x  ∠APB e.g. If  ∠AOB  = 50°,  then according to the property,  ∠APB  = 25°. In Geometry, there is a property which states  However for this proof, it is assumed that we are always able to draw a straight line (i.e. POC) which passes through the centre  O , and cuts both  ∠AOB  and  ∠APB .
A B P O But what you were given this figure where it is impossible to draw a straight line that passes through the centre O and still can cut both  ∠AOB  and  ∠APB ? How do you proof it then?
Let us show you how to :D
A B P O 1 Extend line AO 2 Draw a line from O to P C
A B P O ∠ AOB  +  ∠BOP  +  ∠POC  = 180° (adj. angles on a straight line) C ∠ BOP  = 180 ° – 2 x  ∠OPB  ∠ OBP  =  ∠OPB (isosceles triangle)  P O
A B P O C ∠ AOB  + 180 ° – 2 x  ∠OPB  +   ∠POC  =   180 ° ∠ OPB  =  ∠OPA  +   ∠APB B P O A ∠ AOB  – 2( ∠OPA  +  ∠APB ) +  ∠POC  = O ∠ AOB  – 2 ∠OPA  – 2 ∠APB  +  ∠POC  = O
A B P O C ∠ POC  = 2 ∠OPA [ ∠OPA  =  ∠OAP (isosceles triangle), ∠ POC  =  ∠OAP  +  ∠OPA (external angles)] B P O C A ∠ AOB  - 2  ∠OPA  - 2  ∠APB  +  ∠POC  = O
A B P O C Therefore… ∠ AOB  = 2  ∠APB PROVEN !! :D
The end :D
[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

More Related Content

What's hot

הדגמת משפט פיתגורס
הדגמת משפט פיתגורסהדגמת משפט פיתגורס
הדגמת משפט פיתגורס
osnatsim
 
March 3 Ambiguous Case1
March 3 Ambiguous Case1March 3 Ambiguous Case1
March 3 Ambiguous Case1
ste ve
 
Njc jh303 group c
Njc jh303 group cNjc jh303 group c
Njc jh303 group c
Khanh Minh Luu
 
Hprec10 1
Hprec10 1Hprec10 1
Hprec10 1
stevenhbills
 
11X1 T07 07 products of intercepts
11X1 T07 07 products of intercepts11X1 T07 07 products of intercepts
11X1 T07 07 products of intercepts
Nigel Simmons
 
Lingkaran ii
Lingkaran iiLingkaran ii
Lingkaran ii
Fitria Dini
 
Airplane Answer
Airplane AnswerAirplane Answer
Airplane Answer
endo_jo
 
Perimeter and area
Perimeter and areaPerimeter and area
Perimeter and area
Nur Endah Purnaningsih
 
Perimeter and area
Perimeter and areaPerimeter and area
Perimeter and area
Nur Endah Purnaningsih
 
To prove that parallelograms on the same base and between the same parallel l...
To prove that parallelograms on the same base and between the same parallel l...To prove that parallelograms on the same base and between the same parallel l...
To prove that parallelograms on the same base and between the same parallel l...
Sitikantha Mishra
 
March 19 Trig Review
March 19 Trig ReviewMarch 19 Trig Review
March 19 Trig Review
ste ve
 
ข้อสอบ Gsp
ข้อสอบ Gspข้อสอบ Gsp
ข้อสอบ Gsp
Kiatmanee Bamrungrai
 
11X1 T13 07 products of intercepts (2010)
11X1 T13 07 products of intercepts (2010)11X1 T13 07 products of intercepts (2010)
11X1 T13 07 products of intercepts (2010)
Nigel Simmons
 
Matematicas criterios
Matematicas criteriosMatematicas criterios
Matematicas criterios
Luis Fernando Flores Sanchez
 
การแปลงทางเรขาคณิต
การแปลงทางเรขาคณิตการแปลงทางเรขาคณิต
การแปลงทางเรขาคณิต
Ruangrit Ritruangdej
 

What's hot (15)

הדגמת משפט פיתגורס
הדגמת משפט פיתגורסהדגמת משפט פיתגורס
הדגמת משפט פיתגורס
 
March 3 Ambiguous Case1
March 3 Ambiguous Case1March 3 Ambiguous Case1
March 3 Ambiguous Case1
 
Njc jh303 group c
Njc jh303 group cNjc jh303 group c
Njc jh303 group c
 
Hprec10 1
Hprec10 1Hprec10 1
Hprec10 1
 
11X1 T07 07 products of intercepts
11X1 T07 07 products of intercepts11X1 T07 07 products of intercepts
11X1 T07 07 products of intercepts
 
Lingkaran ii
Lingkaran iiLingkaran ii
Lingkaran ii
 
Airplane Answer
Airplane AnswerAirplane Answer
Airplane Answer
 
Perimeter and area
Perimeter and areaPerimeter and area
Perimeter and area
 
Perimeter and area
Perimeter and areaPerimeter and area
Perimeter and area
 
To prove that parallelograms on the same base and between the same parallel l...
To prove that parallelograms on the same base and between the same parallel l...To prove that parallelograms on the same base and between the same parallel l...
To prove that parallelograms on the same base and between the same parallel l...
 
March 19 Trig Review
March 19 Trig ReviewMarch 19 Trig Review
March 19 Trig Review
 
ข้อสอบ Gsp
ข้อสอบ Gspข้อสอบ Gsp
ข้อสอบ Gsp
 
11X1 T13 07 products of intercepts (2010)
11X1 T13 07 products of intercepts (2010)11X1 T13 07 products of intercepts (2010)
11X1 T13 07 products of intercepts (2010)
 
Matematicas criterios
Matematicas criteriosMatematicas criterios
Matematicas criterios
 
การแปลงทางเรขาคณิต
การแปลงทางเรขาคณิตการแปลงทางเรขาคณิต
การแปลงทางเรขาคณิต
 

Similar to A) proving angle properties of circles 1

A) proving angle properties of circles 2
A) proving angle properties of circles 2A) proving angle properties of circles 2
A) proving angle properties of circles 2
njcjh305groupc
 
Circles
CirclesCircles
5 similar+triangles%26 power+of+a+point+%28solutions%29
5 similar+triangles%26 power+of+a+point+%28solutions%295 similar+triangles%26 power+of+a+point+%28solutions%29
5 similar+triangles%26 power+of+a+point+%28solutions%29
ponce Lponce
 
Circles
CirclesCircles
Circles
itutor
 
Prove it! (circles)
Prove it! (circles)Prove it! (circles)
Prove it! (circles)
Frank Davis
 
Triangles class 9
Triangles class 9Triangles class 9
Triangles class 9
narenderkumar335
 
Module 1 triangle trigonometry
Module 1  triangle trigonometryModule 1  triangle trigonometry
Module 1 triangle trigonometry
dionesioable
 
Mathematics
MathematicsMathematics
Mathematics
Rohit Kumar
 
Circle.
Circle.Circle.
Circle.
geometry303d
 
Mathematics Project
Mathematics ProjectMathematics Project
Mathematics Project
Siva Suriya
 
Angles
AnglesAngles
Angles
khaloi
 
Slideshare
SlideshareSlideshare
Slideshare
letsenjoy
 
Circle
CircleCircle
Circle
letsenjoy
 
Prove it!
Prove it!Prove it!
Prove it!
Frank Davis
 
Lines and Angles_Lecture_1.pptx
Lines and Angles_Lecture_1.pptxLines and Angles_Lecture_1.pptx
Lines and Angles_Lecture_1.pptx
Resham31
 
Angles in a circle and cyclic quadrilateral --GEOMETRY
Angles in a circle and cyclic quadrilateral  --GEOMETRYAngles in a circle and cyclic quadrilateral  --GEOMETRY
Angles in a circle and cyclic quadrilateral --GEOMETRY
indianeducation
 
Maths
MathsMaths
Maths
Jack527
 
116 coriolis acceleration
116  coriolis acceleration116  coriolis acceleration
116 coriolis acceleration
Aravind Mohan
 
Circle 10 STB.pptx
Circle 10 STB.pptxCircle 10 STB.pptx
Circle 10 STB.pptx
Vinod Gupta
 

Similar to A) proving angle properties of circles 1 (19)

A) proving angle properties of circles 2
A) proving angle properties of circles 2A) proving angle properties of circles 2
A) proving angle properties of circles 2
 
Circles
CirclesCircles
Circles
 
5 similar+triangles%26 power+of+a+point+%28solutions%29
5 similar+triangles%26 power+of+a+point+%28solutions%295 similar+triangles%26 power+of+a+point+%28solutions%29
5 similar+triangles%26 power+of+a+point+%28solutions%29
 
Circles
CirclesCircles
Circles
 
Prove it! (circles)
Prove it! (circles)Prove it! (circles)
Prove it! (circles)
 
Triangles class 9
Triangles class 9Triangles class 9
Triangles class 9
 
Module 1 triangle trigonometry
Module 1  triangle trigonometryModule 1  triangle trigonometry
Module 1 triangle trigonometry
 
Mathematics
MathematicsMathematics
Mathematics
 
Circle.
Circle.Circle.
Circle.
 
Mathematics Project
Mathematics ProjectMathematics Project
Mathematics Project
 
Angles
AnglesAngles
Angles
 
Slideshare
SlideshareSlideshare
Slideshare
 
Circle
CircleCircle
Circle
 
Prove it!
Prove it!Prove it!
Prove it!
 
Lines and Angles_Lecture_1.pptx
Lines and Angles_Lecture_1.pptxLines and Angles_Lecture_1.pptx
Lines and Angles_Lecture_1.pptx
 
Angles in a circle and cyclic quadrilateral --GEOMETRY
Angles in a circle and cyclic quadrilateral  --GEOMETRYAngles in a circle and cyclic quadrilateral  --GEOMETRY
Angles in a circle and cyclic quadrilateral --GEOMETRY
 
Maths
MathsMaths
Maths
 
116 coriolis acceleration
116  coriolis acceleration116  coriolis acceleration
116 coriolis acceleration
 
Circle 10 STB.pptx
Circle 10 STB.pptxCircle 10 STB.pptx
Circle 10 STB.pptx
 

A) proving angle properties of circles 1

  • 1. (a) Proving Angle Properties of Circles
  • 2. A B P O C that the angle subtended by an arc at the centre of a circle is twice that subtended at the circumference of the same circle .  ∠ AOB = 2 x ∠APB e.g. If ∠AOB = 50°, then according to the property, ∠APB = 25°. In Geometry, there is a property which states However for this proof, it is assumed that we are always able to draw a straight line (i.e. POC) which passes through the centre O , and cuts both ∠AOB and ∠APB .
  • 3. A B P O But what you were given this figure where it is impossible to draw a straight line that passes through the centre O and still can cut both ∠AOB and ∠APB ? How do you proof it then?
  • 4. Let us show you how to :D
  • 5. A B P O 1 Extend line AO 2 Draw a line from O to P C
  • 6. A B P O ∠ AOB + ∠BOP + ∠POC = 180° (adj. angles on a straight line) C ∠ BOP = 180 ° – 2 x ∠OPB ∠ OBP = ∠OPB (isosceles triangle) P O
  • 7. A B P O C ∠ AOB + 180 ° – 2 x ∠OPB + ∠POC = 180 ° ∠ OPB = ∠OPA + ∠APB B P O A ∠ AOB – 2( ∠OPA + ∠APB ) + ∠POC = O ∠ AOB – 2 ∠OPA – 2 ∠APB + ∠POC = O
  • 8. A B P O C ∠ POC = 2 ∠OPA [ ∠OPA = ∠OAP (isosceles triangle), ∠ POC = ∠OAP + ∠OPA (external angles)] B P O C A ∠ AOB - 2 ∠OPA - 2 ∠APB + ∠POC = O
  • 9. A B P O C Therefore… ∠ AOB = 2 ∠APB PROVEN !! :D
  • 11.