Question

what is the x and y points for -4pi/5

Answer 1

I assume you mean what is rcos(theta) and rsin(theta)
where x=rcos(theta) and y=rsin(theta)
?

Answer 2

YES

Answer 3

Plug in theta=-4pi/5 and evaluate based on the unit circle
You might wwant to do -4pi/5+2pi if you prefer to look at positives

Answer 4

You may have use identities before using that chart
unless you are able to approximate x and y .