The angle of elevation of the top of a tower, vertically erected in the middle of a paddy field, from two points on a horizontal line through the foot of the tower are given to be α and β (α>β). The height of the tower is h unit. A possible distance (in the same unit) between the points is 1.    h(cotβ – cota) / cos(a + β) 2.    h (cota – cotβ) 3.    h (tanβ – tana) / tana + tanβ 4.    h (cata + cotβ)