Ans is B 30
since AB is equal to the radius of the circle triangle OAB is equilateral. hence angle AOB is 60
x=1/2*angle AOB=30
readyforgmat geometry problem
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vinaynp
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I understand the equilateral part. But, how is x=1/2*angle AOB=30. Which property is this? Yes, the answer is Bliferocks wrote:Ans is B 30
since AB is equal to the radius of the circle triangle OAB is equilateral. hence angle AOB is 60
x=1/2*angle AOB=30
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Nilakshi1001
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Here, the AB is equal to the Radius. So if we draw a triangle with AB as the base and the third vertex as the centre O, we get a triangle AOB. Now Angle x and Angle AOB is made by the same base AB.
Now we know angle at the centre of the circle is twice the angle at the circumference.
or, angle AOB = 2* angle x
Now, triangle AOB is equilateral.
60 = 2*x
or, x=30
Thus B
Now we know angle at the centre of the circle is twice the angle at the circumference.
or, angle AOB = 2* angle x
Now, triangle AOB is equilateral.
60 = 2*x
or, x=30
Thus B
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vinaynp
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I still don't get the part about the angle at the center of the circle is twice the angle at the circumference.Nilakshi1001 wrote:Here, the AB is equal to the Radius. So if we draw a triangle with AB as the base and the third vertex as the centre O, we get a triangle AOB. Now Angle x and Angle AOB is made by the same base AB.
Now we know angle at the centre of the circle is twice the angle at the circumference.
or, angle AOB = 2* angle x
Now, triangle AOB is equilateral.
60 = 2*x
or, x=30
Thus B
.I am doing math after 8 years..I want to know the theory ..I know that inscribed angle of a diameter is 90 degrees.-
liferocks
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this is the theory behind 'the angle at the center of the circle is twice the angle at the circumference'.Let me know if it clarifies the questions.
here angle AOB=2(x+y)=angle ACB
here angle AOB=2(x+y)=angle ACB
Last edited by liferocks on Tue Apr 27, 2010 10:45 pm, edited 1 time in total.
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