Question

If a+b=45° then prove that (1+tana)(1+tanb)=2 hence find tan (45/2)

Answer 1

Given A+B=45
{Take tan on both the sides }

tan(A+B) = tan45

tanA+tanB/1- tanA tanB = 1

tanA+tanB=1-tanA.tanB

tanA+tanB+tanA.tanB=1

adding "1" on both sides

1+ tanA+tanB+tanA.tanB=1+1

(1 + tanA)+tanB(1+tanA).=2

(1+tanA)(1+tanB)=2 Hence proved .

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