# Need help with double angle identity questions.

#### hayling123

##### New member
Hey guys,

I'm working my way through some problems and have become stuck on the following questions-

"Use the double-angle identity for tangent, and the exact value of tan(5π/6), for a different way to find an exact value of tan(5π/12)."

I have already shown the exact value of tan(5π/12) is 2+sqrt3

Any help with how i'd go about it would be great. I know I will need to solve a quadratic equation, but any help to get there would be fantastic

cheers

#### BigBeachBanana

##### Full Member
$\tan\left(\frac{5\pi}{6}\right)=\tan\left(2\cdot\frac{5\pi}{12}\right)$Can you use the double-angle identity to continue?

#### Jomo

##### Elite Member
I have already shown the exact value of tan(5π/12) is 2+sqrt3
Can you show how you got tan(5π/12) = 2+sqrt3?