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

so

tan(v) = 0.5 / 0.87

v = atan(0.5/0.87)

atan(0.5/0.87) = 29.886526940424

v=29.88 degrees