Bisect the angle to get 30 deg + 30 deg.
Bisect the 30 deg angle to get 15 deg + 15 deg.
Bisect the 15 deg angle to get 7.5 deg + 7.5 deg.
Thus the final angle is 7.5 deg.
If u want only steps of construction this is one of the method:Draw a line segmnt AB=7.5 Extend the line from B to 1unit i.e 1cm , mark it as C.Draw perpendicular of AC,Mark it as O.Draw semi circle of AC from O.Draw an angle of 90° from B.From B draw an arc taking point on the semicircle.Draw the arc from B on the no.lineIt will be ur root 7.5
Hope it helps u...