If Sin alpha × sin bita - cos alpha × cos bita = 1 show that tan alpha+tan bita =0

Sin alpha × sin bita - cos alpha × cos bita = 1=> - Cos( alpha+beta) =1=> Cos( alpha+ beta) =-1So Sin( alpha+ beta) =0And tan(( alpha+ beta) =0USE FORMULA for tan(a+b)This tanalpha + tanBETA =0