When n = 1, tan x1 = 1.414 and similarly when n=2 tanx1 + tanx2 = 2
which implies tan x2 = 0.586.
from these values of tan cos x1 = 0.577 and cos x2 = 0.862
since x belogs to 0 to pi/2 , thus cosx can have a maximum of value 1.
add cos x1+ cos x2 > 1 which implies the least positive value of k would be 0.577. reply if still not satisfied! 