



 
Hi Graham, Angles are usually measured in a counterclockwise directionso I am going to assume that the rectangle is rotated 50 degrees counterclockwise around the centre of the circle wich is also the origin. Here are my diagrams of the rectangle and the rotated rectangle.
You now have a point (x, y) in the plane and you want to check to see if it is inside the rotated rectangle. I would take the point (x, y), rotate it 50 degrees clockwise around the centre of the circle and then check to see if the resulting point is inside the original rectangle. Suppose that you have a point (x, y) in the plane and and you want to rotate it degrees counterclockwise around the origin to arrive at a new point (x', y') then the relationship between (x, y) and (x', y') is
In your situation you want to rotate the point 50^{o} clockwise so =  50^{o}. Start with the point in question, (x, y), transform it to (x', y') by
and check to see if (x', y') is in the original rectangle. Penny  


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