inverse cos is the same as arc cos
The vertical red line is 0.5 units and it is opposite the angle that you want
The horozontal part of the right triangle is 0.87 units long and that is the adjacent side.
tan = opp/hyp
tan(v) = 0.5 / 0.87
v = atan(0.5/0.87)
atan(0.5/0.87) = 29.886526940424