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put this solution on YOUR website! .
From the measure 765 degrees, subtract the full rotation angle of 360 degrees so many times to get the difference between 0 and 360 degrees.
In your case, it is necessary and sufficient to subtract 360 degrees from 765 degrees TWICE
to get the coterminal angle of 765 - 2*360 = 45 degrees.
The angle is in the first quadrant.
Solved and explained.