(cos(B+15) - cosB*cos15) / (sin B * cos 15) =
(cosB*cos15 - sinB*sin15 - cosB*cos15) / (sin B * cos 15) =
- sinB*sin15 / (sin B * cos 15) = -sin15 / cos 15 = -tg15 = V3 - 2
(cosBcos15 - sinBsin15 - cosBcos15) / (sinBsin15)
(-sinBsin15) / (sinBsin15) = -1
