You should assume radians. Radians are, in general, superior.
Especially when working with Calculus and Differential Equations. The laws and are only true for x in radians.
(In fact, the definitions of sine and cosine that you should be using at this point do not require that x be an angle at all- should not even have units just as you don't worry about the units for "x" in - but in order to connect to the "old" trigonometric definitions (and keep the engineers happy), we can think of x as being in "radians".)