I am stumped with this Grade 11 circle challenge.

I'm supposed to find 'r' but no measurements are given. Can I get clues?

http://img23.imageshack.us/img23/5686/findingr.jpg

thanks!!

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- April 3rd 2009, 06:37 PMnathan02079Radius of circle inside a circle
I am stumped with this Grade 11 circle challenge.

I'm supposed to find 'r' but no measurements are given. Can I get clues?

http://img23.imageshack.us/img23/5686/findingr.jpg

thanks!! - April 3rd 2009, 11:08 PMred_dog
=the center of the big circle. =the center of the small circle.

Let the radius tangent to the small circle. In the figure it seems that the radius are perpendicular.

Let .

In the triangle apply Pitagora: