# Math Help - Exact value for ratio

1. ## Exact value for ratio

Hey i need help finding the exact measures for these two trig ratios

cot(4pi/3)
cos(-19pi/6)

2. ## Re: Exact value for ratio

Well, how would you solve $\tan{\frac{4\pi}{3}}$? Can you think of anything equivalent to this? Think of the unit circle - which other value for tan will give an equivalent result?

For $\cos{(\frac{-19\pi}{6})}$, it's the same idea. Remember that $\cos(x)$ is periodic every $2\pi$ radians, so you can keep adding $\frac{12}{6}\pi$ to the value in the brackets and your answer will be unchanged.

3. ## Re: Exact value for ratio

I bet a diagram of the unit circle will help, too.
See the one on Wikipedia here.