# 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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