The radian (rad) is a unit for measuring angles: it is equal to 180°/π, so that the magnitude of an angle of 180° can be expressed as "π radian". Often the word "radian" is omitted, as it is implied that when the amplitude of an angle is expressed without a unit of measurement it is represented in radians: saying that an angle is 90° wide is equivalent to saying that it is π/2 wide.

 

The values are rounded. In the last example yA is 2+√3. The exact value of the angle [of dir BA] is 120° [60°].
I valori sono arrotondati. Nell'ultimo esempio yA è 2+√3. Il valore esatto dell'angolo [della direzione di BA] è 120° [60°].