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Circles iv

  1. Find the values of the unknown letters.

Theorem 9 Two tangents drawn to a circle from the same point outside the circle are equal in length.

Proof :

Consider a circle, with centre O . Choose a point P outside the circle. Draw two tangents to the circle from point P , that meet the circle at A and B . Draw lines O A , O B and O P . The aim is to prove that A P = B P . In O A P and O B P ,

  1. O A = O B (radii)
  2. O A P = O P B = 90 ( O A A P and O B B P )
  3. O P is common to both triangles.

O A P O B P (right angle, hypotenuse, side) A P = B P

Circles v

  1. Find the value of the unknown lengths.

Theorem 10 The angle between a tangent and a chord, drawn at the point of contact of the chord, is equal to the angle which the chord subtends in the alternate segment.

Proof :

Consider a circle, with centre O . Draw a chord A B and a tangent S R to the circle at point B . Chord A B subtends angles at points P and Q on the minor and major arcs, respectively. Draw a diameter B T and join A to T . The aim is to prove that A P B ^ = A B R ^ and A Q B ^ = A B S ^ . First prove that A Q B ^ = A B S ^ as this result is needed to prove that A P B ^ = A B R ^ .

A B S ^ + A B T ^ = 90 ( TB SR ) B A T ^ = 90 ( 's at centre ) A B T ^ + A T B ^ = 90 ( sum of angles in BAT ) A B S ^ = A B T ^ However, AQB ^ = A T B ^ ( angles subtended by same chord AB ) A Q B ^ = A B S ^ S B Q ^ + Q B R ^ = 180 ( SBT is a str. line ) A P B ^ + A Q B ^ = 180 ( ABPQ is a cyclic quad ) S B Q ^ + Q B R ^ = A P B ^ + A Q B ^ AQB ^ = A B S ^ A P B ^ = A B R ^

Circles vi

  1. Find the values of the unknown letters.

Theorem 11 (Converse of [link] ) If the angle formed between a line, that is drawn through the end point of a chord, and the chord, is equal to the angle subtended by the chord in the alternate segment, then the line is a tangent to the circle.

Proof :

Consider a circle, with centre O and chord A B . Let line S R pass through point B . Chord A B subtends an angle at point Q such that A B S ^ = A Q B ^ . The aim is to prove that S B R is a tangent to the circle. By contradiction. Assume that S B R is not a tangent to the circle and draw X B Y such that X B Y is a tangent to the circle.

A B X ^ = A Q B ^ ( tan - chord theorem ) However , ABS ^ = A Q B ^ ( given ) A B X ^ = A B S ^ But , ABX ^ = A B S ^ + X B S ^ can only be true if , XBS ^ = 0

If X B S ^ is zero, then both X B Y and S B R coincide and S B R is a tangent to the circle.

Applying theorem [link]

  1. Show that Theorem [link] also applies to the following two cases:

B D is a tangent to the circle with centre O . B O A D . Prove that:
  1. C F O E is a cyclic quadrilateral
  2. F B = B C
  3. C O E / / / C B F
  4. C D 2 = E D . A D
  5. O E B C = C D C O

  1. F O E ^ = 90 ( BO OD ) F C E ^ = 90 ( subtended by diameter AE ) C F O E is a cyclic quad ( opposite 's supplementary )
  2. Let O E C ^ = x .

    F C B ^ = x ( between tangent BD and chord CE ) B F C ^ = x ( exterior to cyclic quad CFOE ) B F = B C ( sides opposite equal 's in isosceles BFC )
  3. C B F ^ = 180 - 2 x ( sum of 's in BFC ) O C = O E ( radii of circle O ) E C O ^ = x ( isosceles COE ) C O E ^ = 180 - 2 x ( sum of 's in COE )
    • C O E ^ = C B F ^
    • E C O ^ = F C B ^
    • O E C ^ = C F B ^
    C O E ||| C B F ( 3 's equal )
    1. In E D C

      C E D ^ = 180 - x ( 's on a str. line AD ) E C D ^ = 90 - x ( complementary 's )
    2. In A D C

      A C E ^ = 180 - x ( sum of 's ACE ^ and ECO ^ ) C A D ^ = 90 - x ( sum of 's in CAE )
    3. Lastly, A D C ^ = E D C ^ since they are the same .

    4. A D C ||| C D E ( 3 's equal ) E D C D = C D A D C D 2 = E D . A D
    1. O E = C D ( OEC is isosceles )
    2. In B C O

      O C B ^ = 90 ( radius OC on tangent BD ) C B O ^ = 180 - 2 x ( sum of 's in BFC )
    3. In O C D

      O C D ^ = 90 ( radius OC on tangent BD ) C O D ^ = 180 - 2 x ( sum of 's in OCE )
    4. Lastly, O C is a common side to both 's.

    5. B O C ||| O D C ( common side and 2 equal angles ) C O B C = C D C O O E B C = C D C O ( OE = CD isosceles OEC )

F D is drawn parallel to the tangent C B Prove that:
  1. F A D E is cyclic
  2. A F E ||| C B D
  3. F C . A G G H = D C . F E B D

  1. Let B C D = x

    C A H = x ( between tangent BC and chord CE ) F D C = x ( alternate , FD CB ) FADE is a cyclic quad ( chord FE subtends equal 's )
    1. Let F E A = y

      F D A = y ( 's subtended by same chord AF in cyclic quad FADE ) C B D = y ( corresponding 's, FD CB ) F E A = C B D
    2. B C D = F A E ( above )
    3. A F E = 180 - x - y ( 's in AFE ) C B D = 180 - x - y ( 's in CBD ) A F E ||| C B D ( 3 's equal )
    1. D C B D = F A F E D C . F E B D = F A
    2. A G G H = F A F C ( FG CH splits up lines AH and AC proportionally ) F A = F C . A G G H
    3. F C . A G G H = D C . F E B D

Questions & Answers

anyone know any internet site where one can find nanotechnology papers?
Damian Reply
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
many many of nanotubes
what is the k.e before it land
what is the function of carbon nanotubes?
I'm interested in nanotube
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Siyavula textbooks: grade 12 maths. OpenStax CNX. Aug 03, 2011 Download for free at http://cnx.org/content/col11242/1.2
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