reference angle for -19pi/6?

I get confused whether to use one pi , or 2 pi , or 4 pi? I don't when to use it.
I understand how to sketch the angle , and find the degree of it but then I get lost with the radians.

My notes say the reference is 5pi/6 ? how did they get that ?

\(\bf \cfrac{19}{6}\implies 3+\cfrac{1}{6} \\ \quad \\\\ \cfrac{-19\pi }{6}\implies -\left(3\pi +\cfrac{1\pi }{6} \right)\impliedby clockwise \\ \quad \\\\ or\implies -\left(2\pi +\pi +\cfrac{\pi }{6} \right)\)

go that much "clockwise", you'll end up at the 2nd quadrant,
the reference angle, is its reflective angle on the 1st quadrant

Answer Link

reference angle for -19pi/6? I get confused whether to use one pi , or 2 pi , or 4 pi? I don't when to use it. I understand how to sketch the angle , and find the degree of it but then I get lost with the radians.My notes say the reference is 5pi/6 ? how did they get that ?

Verified Answer :

Related Questions

reference angle for -19pi/6?

I get confused whether to use one pi , or 2 pi , or 4 pi? I don't when to use it.
I understand how to sketch the angle , and find the degree of it but then I get lost with the radians.

My notes say the reference is 5pi/6 ? how did they get that ?