How to prove \(\displaystyle{\tan{{x}}}+{\tan{{\left({x}+{\frac{{\pi}}{{{3}}}}\right)}}}+{\tan{{\left({x}+{\frac{{{2}\pi}}{{{3}}}}\right)}}}={3}{\tan{{3}}}{x}\)

Albert Byrd

Albert Byrd

Answered question

2022-04-09

How to prove
tanx+tan(x+π3)+tan(x+2π3)=3tan3x

Answer & Explanation

razmenile7chp

razmenile7chp

Beginner2022-04-10Added 11 answers

Let
tan3x=tan3A
3x=nπ+3A, x=nπ3+A where n is any integer
We can set x=A,π3+A,2π3+A
Now,
tan3A=tan3x=3tanxtan3x13tan2x
On rearrangement
tan3x3tan3Atan2x3tanx+tan3A=0
which is a cubic equation in tanx
Now, apply Vieta's formula to find
tanx=3tan3A, tanx=tan3A

Do you have a similar question?

Recalculate according to your conditions!

Ask your question.
Get an expert answer.

Let our experts help you. Answer in as fast as 15 minutes.

Didn't find what you were looking for?