Hey i need help finding the exact measures for these two trig ratios
cot(4pi/3)
cos(-19pi/6)
Well, how would you solve $\displaystyle \tan{\frac{4\pi}{3}}$? Can you think of anything equivalent to this? Think of the unit circle - which other value for tan will give an equivalent result?
For $\displaystyle \cos{(\frac{-19\pi}{6})}$, it's the same idea. Remember that $\displaystyle \cos(x)$ is periodic every $\displaystyle 2\pi$ radians, so you can keep adding $\displaystyle \frac{12}{6}\pi$ to the value in the brackets and your answer will be unchanged.