Rizwans new maths step....[Amazing stuff]

Venue : Sreekumar sir's tution
Sir gave the problem:to prove cos'{cosA+cosB/1+cosAcosB}=2tan'{tanA/2.tanB/2}
Rizwan: Hahaha this is simple!!
Athul: Vot??
Rizwan: Ayye etine mottattil oru cosA vechu numeraterineyum dinominaterineyum divide cheyta mathi
Athul: Manda! appo second term complex aavum
Rizwan: Poda kappa, cosB ye Cos A vechu divide cheytal pore?
Athul: Atalle njan paranje ath (cosB/cosA) aayitt kidakkumenn.
Rizwan: Ayye!( cosB) ye (cos A) vechu divide cheytal Cot (B/A) avuleda manda!! etu polum arinjudengil nee poi chattu kala!!

Vot to do guys? paavam ee edayayi pulli alpam loosaanu...