Given:

Question

x+(1/x)= square root of 3

PROVE:
(x^13)+(1/(x^13))= square root of 3

Answer 1

Put x = exp(i t)

Then:

x + 1/x = 2 cos(t)

x + 1/x = sqrt(3) ---->

cos(t) = sqrt(3)/2 ---->

t = ±pi/6 (adding a multiple of 2 pi leaves x invariant)

x^(13) + x^(-13) = 2 cos(13 t) =

2 cos(13/6 pi) = 2 cos(pi/6) = sqrt(3)