Prove , if x is a rational number , x ≠ 0 then , tan(x) is not rational

[Maths Lover]

prove , if x is a rational number , x ≠ 0 then , tan(x) is not rational

this theorem was proved by a mathematician called Lambert ,
I search for the proof , anyone knows it ?!

 

[pwsnafu]

Are you asking for Lambert original proof? Wikipedia has a sketch of Laczkovich's simplification.

 

[JsStewartFan]

http://en.wikipedia.org/wiki/Proof_that_π_is_irrational#Lambert.27s_proof

Sorry - same page as above.