The periodic nature of the trig functions means that we can reduce 390 degrees by 360 (a whole revolution), so that it is in the range 0 to 360. So 390 is the same as 30 for these purposes. sin30=1/2; cos30=sqrt(3)/2; tan30=1/sqrt(3) or sqrt(3)/3; cot(30)=sqrt(3); sec30=2/sqrt(3) or 2sqrt(3)/3; cosec(30)=2. All these values apply to 390.