Can you solve this kind of problem on a TI-89 Calc? finding trig angle

I am wanting to know if there is any way that you can solve the following problem by just using your calculator?

Find Exact values using combination of $\displaystyle \frac{\pi}{6}$,$\displaystyle \frac{\pi}{6}$

1. $\displaystyle tan(\frac{\pi}{12})$

2. $\displaystyle sin(\frac{5\pi}{12})$

3. $\displaystyle cos(\frac{11\pi}{12})$

I am looking for a quick and easy way to solve these kinds of problems, just thought that someone could help me!!

Thanks

RE: Are these answers correct?

Quote:

Originally Posted by

**qbkr21** I mean I know how to use the half angle formula, but given values such as $\displaystyle \frac{\pi}{6}$ and $\displaystyle \frac{\pi}{4}$ how can I figure figure out which value to use in the formula. This off all would help me out the most....

Thanks So Much!

Are these answers right and acceptable?

1. $\displaystyle tan(\frac{\pi}{12})$

=$\displaystyle -(\sqrt{3}-2)$

2. $\displaystyle sin(\frac{5\pi}{12})$

=$\displaystyle \frac{(\sqrt{3}+1)*\sqrt{2}}{4}$

3.$\displaystyle cos(\frac{11\pi}{12})$

=$\displaystyle \frac{-(\sqrt{3}+1)*\sqrt{2}}{4}$

Thanks for the help!!