if A+B=45 degree.show that {1+tanA}{1+tanB}=2
A+B=45
tan(A+B)= tan45
tanA+tanB/1- tanAtanB=1
tanA+ tanB= 1-tanAtanB
tanA +tanB+ tanAtanB=1
1+tanA +tanB+ tanAtanB=1+1 (adding 1 on both sides)
1(1+tanA) +tanB(1+tanA) =2
(1+tanA)(1+tanB)=2
HENCE, PROVED.