Two lines intersect at $O$ at an angle of $60^\circ$. Two circles are drawn such that they are tangent to each other and the two lines. $A$ and $B$ are the centers of the smaller and the larger circle, respectively. If the radius of the smaller circle is $15$, what is the length of $OB$?

[Moderator-tip: Use \$ instead of \( A for inline math.]

## Circle circle

- Fatin Farhan
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### Circle circle

Last edited by Phlembac Adib Hasan on Sun Apr 21, 2013 12:38 pm, edited 2 times in total.

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### Re: Circle circle

Its a tedious work to illustrate the whole thing.Just the outline here.

1.Complete the equilateral triangle where the small circle is inscribed and find the length of sides of the triangle.

2.draw perpendiculars from the centers to the lines (lines that are mentioned in the que.)

3.Joint every vertice of the triangle (see1.) to the centre $B$.

Observe the figure for a minute or two.You have got it? Hmm..Good. now just finish it man!

1.Complete the equilateral triangle where the small circle is inscribed and find the length of sides of the triangle.

2.draw perpendiculars from the centers to the lines (lines that are mentioned in the que.)

3.Joint every vertice of the triangle (see1.) to the centre $B$.

Observe the figure for a minute or two.You have got it? Hmm..Good. now just finish it man!

An amount of certain opposition is a great help to a man.Kites rise against,not with,the wind.