Ascending Crescent

Geometry Level 2

Diagram above shows two circles are tangent internally to each other. The straight lines \(AB\) and \(CD\) are perpedicular and the point \(O \) is the center of the larger circle. The length of straight lines \(AP \) and \(CQ\) are \(4\text{ cm} \) and \(3\text{ cm} \) respectively. What is the radius of the smaller circle?

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