so hmmm notice [tex]\bf sin(\theta)=\cfrac{opposite}{hypotenuse}\implies sin(\theta)=\cfrac{-4\leftarrow opposite}{5\leftarrow hypotenuse}[/tex]
they hypotenuse, is just the radius, thus is never negative, since it's just a unit
now, check the picture below, that's the angle, and its reference angle
so.. use the pythagorean theorem to get the adjacent side, or "x" value
keeping in mind that [tex]\bf tan(\theta)=\cfrac{opposite}{adjacent}
=\cfrac{y}{x}
\qquad \qquad sec(\theta)=\cfrac{hypotenuse}{adjacent}
=\cfrac{r}{x}[/tex]
