The obtuse angle SUV can be measured anti-clockwise from the line SU to get 120°. Then, subtract this angle from 360° to find the reflex angle.

Obtuse. An obtuse angle is an angle that is bigger than 90° degrees, but doesn’t reach a straight line at 180°. Image caption, Straight line. A straight line is 180˚ ...

If an angle is greater than 90 degrees, but less than 180 degrees, it's called an obtuse angle. ...