Every point on the unit circle is defined as $(\cosθ,\sinθ)$.
Where is $180^\circ$ on the unit circle?
Where is the $y-$value at that point?

See part (a).

When an angle is negative, it opens clockwise from $0^\circ$ on the unit circle.

Find an equivalent angle between $0^\circ\ \text{and}\ 360^\circ$ by subtracting $510 − 360$. Notice that the reference triangle is a $30^\circ-60^\circ-90^\circ$ triangle. Find the $\sin30^\circ$.

What is the $x-$value in this location?

Remember the tangent is the ratio of $\frac{y}{x}$.