For angles ranging from 0 to 360,

Sin(angle) may be viewed as the y co-ordinate of a point on a unit circle,

of radius 1.

If 2x is the angle,

where is the y co-ordinate -1 ?

answer: at 270 degrees, or

Sin(270 degrees)= -1.

So 2x is 270 degrees or 270+n(360) degrees, n=0,1,2,3........

x is

The second result is obtained for 2x=270+360 degrees,

as x<360 degrees.