# Area between concentric circles [closed]

We are given two concentric circles k1 and k2. Chord t=10cm of the bigger circle is tangent of the smaller circle. Find the area of ring between two circles.

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What have you tried so far? –  Dylan Yott Jun 16 at 16:06
Do you need to exclude the area of the Larger circle formed by the chord t and the arc at which t intersects the larger circle, from the area of the ring? –  amWhy Jun 16 at 16:10

## closed as too localized by Danny Cheuk, Amzoti, Zev Chonoles, O.L., Davide GiraudoJun 16 at 16:44

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If the radius of the larger circle be $b$ cm, and that of the smaller one is $a$ cm
Using this and Pythagoras theorem, $b^2=a^2+5^2$
The area of the ring $=\pi(b^2-a^2)$ cm$^2$