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If ABC is a quarter circle and a circle is inscribed in it and if AB=

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If ABC is a quarter circle and a circle is inscribed in it and if AB= [#permalink]

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If ABC is a quarter circle and a circle is inscribed in it and if AB= 1 cm, find radius of inner circle.


A. \(\sqrt{2}- 1\)

B. \(\frac{\sqrt{2}+1}{2}\)

C. \(\frac{\sqrt{2}- 1}{2}\)

[Reveal] Spoiler:
Attachment:
GEOMETRY 6.JPG
GEOMETRY 6.JPG [ 9.99 KiB | Viewed 2463 times ]
[Reveal] Spoiler: OA

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Re: If ABC is a quarter circle and a circle is inscribed in it and if AB= [#permalink]

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New post 04 Oct 2009, 15:24
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If ABC is a quarter circle and a circle is inscribed in it and if AB= 1 cm, find radius of inner circle.


A. \(\sqrt{2}- 1\)

B. \(\frac{\sqrt{2}+1}{2}\)

C. \(\frac{\sqrt{2}- 1}{2}\)


R radius of big circle=1, r radius of inscribed circle.

Diagonal of a square made of \(r=r*\sqrt{2}\)

\(R=1= r*\sqrt{2}+r\) --> \(r=\frac{1}{(\sqrt{2}+1)}=\sqrt{2}-1\)

Answer: A.
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Re: If ABC is a quarter circle and a circle is inscribed in it and if AB= [#permalink]

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New post 01 Nov 2010, 02:03
Bunuel, could you please explain this:

Quote:
R=1= r*\sqrt{2}+r --> r=1/(\sqrt{2}+1)=2^1/2-1

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Re: If ABC is a quarter circle and a circle is inscribed in it and if AB= [#permalink]

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New post 24 Dec 2010, 07:59
Bunuel wrote:
R radius of big circle=1, r radius of inscribed circle.

Diagonal of a square made of r=r*\sqrt{2}

R=1= r*\sqrt{2}+r --> r=1/(\sqrt{2}+1)=2^1/2-1

A.


Colud not understand this.. can someone help ?

thanks in advance
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Re: If ABC is a quarter circle and a circle is inscribed in it and if AB= [#permalink]

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New post 24 Dec 2010, 08:22
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nonameee wrote:
Bunuel, could you please explain this:

Quote:
R=1= r*\sqrt{2}+r --> r=1/(\sqrt{2}+1)=2^1/2-1

hirendhanak wrote:
Bunuel wrote:
R radius of big circle=1, r radius of inscribed circle.

Diagonal of a square made of r=r*\sqrt{2}

R=1= r*\sqrt{2}+r --> r=1/(\sqrt{2}+1)=2^1/2-1

A.


Colud not understand this.. can someone help ?

thanks in advance


Look at the diagram:
Attachment:
GEOMETRY 6.PNG
GEOMETRY 6.PNG [ 11.76 KiB | Viewed 1905 times ]
Diagonal BO of the square made by the radii of the small circle equals to \(BO=\sqrt{r^2+r^2}=r*\sqrt{2}\);

Now, the radius of the big circle BD equals to \(BO+OD=r*\sqrt{2}+r=1\) --> \(r=\frac{1}{\sqrt{2}+1}=\sqrt{2}-1\)

Answer: A.
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Collection of Questions:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


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Re: If ABC is a quarter circle and a circle is inscribed in it and if AB= [#permalink]

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New post 25 Dec 2010, 09:35
Nice explanation.
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Re: If ABC is a quarter circle and a circle is inscribed in it and if AB= [#permalink]

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New post 25 Dec 2010, 15:53
Oh this one was tough.
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Re: If ABC is a quarter circle and a circle is inscribed in it and if AB= [#permalink]

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Re: If ABC is a quarter circle and a circle is inscribed in it and if AB=   [#permalink] 12 Sep 2017, 01:36
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