Simplifying the LHS of tanA+tanBcotA+cotB=tanAtanB.
tanA+tanBcotA+cotB=sinAcosA+sinBcosBcosAsinA+cosBsinB
=sinAcosB+cosAsinBcosAcosBcosAsinB+sinAcosBsinAsinB
=sin(A+B)sinAsinBsin(A+B)cosAcosB
=tanAtanB
=RHS
If A and B are acute angles such that tan A=12,tan B=13 and tan (A+B)=tan A+tan B1−tan A tan B,find A + B
If A = 20∘ and B = 25∘, Find the value of tanA + tanB + tanAtanB.