Rotating the polygon

Hi,
I have created a polygon in my Widget. When I increment the angle i am rotating the polygon using QMatrix. While rotation the polygon co-ordinates doesn't change. i.e. i can see rotating polygon in the screen, but the co-ordinates of the polygon variable and co-ordinate of the rotated polygon which appears in the screen is different.
So my question is how can i get rotated polygon's co-ordinates ???

Thanks

Code:

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polygon = matrix.map( polygon );

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