Angles and right-angled triangles

There is a simple model for measuring signals: the circle containing a right-angled triangle:

1. The hypotenuse corresponds to the radius of the circle.
2. The vertical side corresponds to the magnitude (instantaneous amplitude) of the signal.
3. The angle between the hypotenuse and the horizontal side corresponds to the phase.
4. The right-angled triangle may be uniquely described by pairs of values, of which at least one must be the length of a side, and the other may be one of the other two angles:
   1. 
   2. h-side, v-side
   3. ...