In the Natural Units environment, the arguments for the trigonometric or hyperbolic functions can be unit-free, in which case the argument is assumed to be given in terms of radians, or multiplied by a unit of angle with the dimension length/length(radius).  An error is returned if the dimension of the argument is not an angle.

If the argument has a unit of angle, it is converted to a free expression in the call to the corresponding global function.  Therefore, a call to sin(7*deg) returns as sin(7/180*Pi), because  degree equals  radians.

For other properties, see the global functions in the trig help page.