Question

How do i decide which reference triangle to use for sin-1 (sin 3pi/10)?

Answer 1

Do you mean\[\sin^{-1} (\sin \frac{ \pi }{ 10 })\]?

Answer 2

oops 3pi/10

Answer 3

yes I do

Answer 4

First, make sure that the angle is in the domain of the inverse sine function [-2pi,2pi].

Then remember that the sin generates a number, and inverse sin generates an angle - in this case the same angle you took the sin of.