Trig questions

I expect that angle O is meant to be the reflrex one starting at the poitive x axis and rotating anticlockwise to the point (-6,-8)

The radius (hypotenuse) is 10. 

sin is always given by the y value. The y value is the opposite.

  Sin O =  -8/10 = -0.8

I think the 0 is meant to be a Ø just he could not find the symbol for it. I have seen this question before.

We answered it as a symbol.

By the way, the third last button in the bottom ribbon will bring up symbols that you can use.

Ø is one of them.