X0 = 0

P(N)   VL = sqrt(1 + (Xn-1)^2) = HL = sqrt(n)
P(1)   VL = Xn = sqrt(1 + (X1-1)^2) = sqrt(1 + X0^2) = sqrt(1 + 0^2) = HL =  sqrt(n) =  sqrt(1)   funkar
p(n+1) VL = sqrt(1 + (Xn)^2) = sqrt(1 + n) = HL = sqrt(n + 1)

Xn = sqrt(n) => (Xn)^2 = n