code: public double radAngle(TermAngle spec)
      {
          float nval = spec.getValue();
          final TermLength.Unit unit = spec.getUnit();
          if (spec instanceof TermCalcAngleImpl)
          {
              final CalcArgs args = ((TermCalc) spec).getArgs();
              return args.evaluate(getRadEval());
          }
          else
          {
              if (unit == null)
                  return 0;
              switch (unit)
              {
                  case deg:
                      return (nval * Math.PI) / 180.0; 
                  case grad:
                      return (nval * Math.PI) / 200.0;
                  case rad:
                      return nval;
                  case turn:
                      return nval * 2 * Math.PI;
                  default:
                      return 0;
              }
          }
      }
docs: Converts an angle from a CSS angle to 'rad'.
  @param spec the CSS angle specification
  @return the corresponding angle in radians