Question 77340
Draw the picture.
Comment:I assumed you were rotating into the 3rd quadrant.

Let the new point be P(x,y)
Draw a segment from P to the x axis; that has length y
You now have a right triangle with a 60 degree angle at the origin.
The 3rd angle, at point P, is a 30 degree angle.
x=1cos(240)=-1/2
y=1sin(240)= (-sqrt3)/2
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Cheers,
Stan H.