Circles having the same centre but with different radii are said to be concentric circles. Two circles are said to be equal or congruent if they have equal radii.

A circle passing through all the vertices of a polygon is called a circumscribed circle of the polygon and its centre is called a circumcentre. The polygon is called an inscribed polygon.

A circle touching all the sides of a polygon is called an inscribed circle of the polygon and its centre is called incentre.

## Circles: Arc and Cyclic Properties PDF

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