Sorry for the wait. For these parametric questions and in some differentiation/integration by u-substitution questions, always rely back on the drawing of trig triangle. There’s no way you can get “exact coordinates” if you use sin-1(-3/5). Also recognise the actual value of θ and put that into the given domain. In this case, θ is -36° which makes both sinθ and tanθ negative while cosθ is always positive for the given domain. So from sinθ=-3/5 you can derive cosθ and tanθ which you can then substitute into Y&X.