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# DS - Geometry

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Senior Manager
Joined: 30 May 2005
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DS - Geometry [#permalink]  05 Jul 2005, 08:17
00:00

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 0 sessions
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Director
Joined: 27 Dec 2004
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Stem doesn't say triangle OBC is right angle thus i'd pick E. Won't be surprised if it's A though assuming triangle OBC is right triangle
Director
Joined: 05 Jan 2005
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(B) ruled out as fola has explained.

I don't know if my approach is reasonable, but when i apply the sine rule (a/sin A = b/sin B) on triangle ADB, and with the info. given in (A), i am able to determine the angles in that triangle. With these values (and with my angles known), i use an imaginery pair of compass to construct the diagram as given and i realise that there is only one value of the radius of the circle that can be determined. How to do that, i don't care, but i only know it can be done.

Click (A), move on and don't look back!
Senior Manager
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This is from a PR test. OA is D but I believe it is wrong. The OE assumed that Triangle OBC is a right triangle.

As for S1, draw a line OA. Let the radius of the circle be r. OA = OB = r. OD = r-2

In right triangle ODA, OD^2 + AD^2 = OA^2

(r-2)^2 + 6^2 = r^2

We can solve for r and get r=10 => Sufficient.
Senior Manager
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Re: DS - Geometry [#permalink]  06 Jul 2005, 07:06
AJB77 wrote:

A.

I've seen quite a few problems based on the concept being tested here, so will try to explain.

Given two vertices of a triangle, there are infine circles which has them as points on their circumference, all of them have centres along the perpendicular bisector of the two vertices. In this diagram since the centre is fixed along a line, there can be only one possible circle. Once this is established , the other parametes of the circle can be found.

HMTG.
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Joined: 04 Mar 2005
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ssap wrote:
A?

Any explanations?

Calculate for OA using the 2 rt triangles OAD & ABD
- Same way as explained by AJB77

For S2 - tringle OBC shld not be assumed to be a rt triangle.
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