You will have to explain whatyoumean by "magnitude" of an angle! One common use of "magnitude" of anumberis "absolute value" but, in that sense, "-300" and "60" definitely do NOT have the same magnitude so apparently that is not what you are. It is, of course, true that 60= 360- 300 so that angles of "-300degrees" and "60degrees" give the same point on the unit circle so that sin(-300)= sin(60) and cos(-300)= cos(60). But that is a rather limited use of angles. I would say that is a property of sine and cosine (they have period 360 degrees) rather than an inherent property of the angles themselves.