Let 10 vertical poles standing at equal distances on a straight line , subtend the same angle of elevation `alpha` at a point O on this line and all the poles are on the same side of O. If the height of the longest pole is h and the distance of foot the smallest pole form O is `alpha` then the distance between two consecutive poles, is

Options

A. `( h sin alpha + a cos alpha)/(9 cos alpha)`
B. `(h cos alpha - a sin alpha)/(9 sin alpha)`
C. `( h sin alpha + a cos alpha)/(9 sin alpha)`
D. `(h cos alpha - a sin alpha)/(9 cos alpha)`

Answer

B