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Circle Geometry

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Circle Geometry

by Brent@GMATPrepNow » Sat Dec 13, 2008 11:29 am
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by agoyal2 » Sat Dec 13, 2008 11:55 am
IMO B.

Take the centre of the circle as O.
The Angle AOB will be 2x. And since AB = AO = BO, AOB is an equilateral traingle, hence 2x = 60 and x=30.
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by Brent@GMATPrepNow » Sat Dec 13, 2008 5:31 pm
Yes, the OA is B

Here's my solution:

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by Tomn » Tue Dec 16, 2008 7:56 pm
Ah yes, you have to remember the equilateral triangle rule...
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by logitech » Tue Dec 16, 2008 9:28 pm
Who knows how to use that 50 degree to solve this problem ? B-)
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by brb588 » Tue Dec 16, 2008 10:09 pm
Brent Hanneson wrote:Yes, the OA is B

Here's my solution:

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Okay, I totally cannot figure this problem out. I realized quickly that there was an equilateral triangle in the circle. However, I have no idea how you reached your fourth statement. Do you mind clarifying it for me?
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by Brent@GMATPrepNow » Tue Dec 16, 2008 11:12 pm
There's a rule in circle geometry stating that if a central angle (from the center) and an inscribed angle (from a point on the circle) both hold/contain the same chord then the central angle is twice the inscribed angle.

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So, if the central angle is 60, then the inscribed angle must be 30

I hope that helps
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by brb588 » Wed Dec 17, 2008 9:56 am
Ah, I could eye that it was 30, but I didn't trust it. Thanks as always.
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Squares inscribed in a Semi Circle - Circle Geometry

by rg2345 » Mon Dec 29, 2008 7:14 am
In the attached question, can we assume that the side of the smaller square is half the side of the larger one? If yes, how?
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Squares inscribed in a Semi Circle
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by gabriel » Fri Jan 02, 2009 8:14 pm
Thread moved to the problem solving section.

Brent thanks for sharing the questions with our community.
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by ronniecoleman » Sun Jan 04, 2009 10:26 pm
IMO B
use theorm:

1. arc subtend double the angle at centre than at any other point..
2. All angles of equilateral triangle are equal
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