Question

find the exact value of $cos 180^circ$ in simplest form with a rational denominator.

Explanation:

Step1: Locate angle on unit circle

The angle $180^\circ$ corresponds to the point $(-1, 0)$ on the unit circle, where the x-coordinate is $\cos\theta$.

Step2: Identify cosine value

For $\cos 180^\circ$, use the x-coordinate of the point.

Answer:

$-1$