What is the value of (2tan(pi/12))/(1-tan^2(pi/12))2tan(π12)1tan2(π12)?

2 Answers
Nov 28, 2016

(2tan(pi/12))/(1-tan^2(pi/12))=1/sqrt32tan(π12)1tan2(π12)=13

Explanation:

As tan(A+B)=(tanA+tanB)/(1-tanAtanB)tan(A+B)=tanA+tanB1tanAtanB

if A=BA=B, we have tan2A=(tanA+tanA)/(1-tanAtanA)tan2A=tanA+tanA1tanAtanA

or tan2A=(2tanA)/(1-tan^2A)tan2A=2tanA1tan2A

Now putting A=pi/12A=π12

we have (2tan(pi/12))/(1-tan^2(pi/12))=tan(2xxpi/12)=tan(pi/6)=1/sqrt32tan(π12)1tan2(π12)=tan(2×π12)=tan(π6)=13

Nov 28, 2016

Using identity tan2theta=(2tantheta)/(1-tan^2theta)tan2θ=2tanθ1tan2θ

we have the Expression

(2tan(pi/12))/ (1-tan^2(pi/12) )2tan(π12)1tan2(π12)

=tan(2xxpi/12)=tan(pi/6)=1/sqrt3=tan(2×π12)=tan(π6)=13