Thread: Rossby Waves dispersion relation

Hello,

I've worked through the derivation of the dispersion relation of Rossby Waves on
Rossby wave - Wikipedia, the free encyclopedia

I've been able to get the dispersion relation correct apart from the sign of the term involving beta, the Rossby parameter. It says there should be a minus sign in front of that term, however I cannot see where the minus sign comes from.

I think there is a mistake in third term