Home > Resources > Homework > Math > Unit Circle

Find the values of $ cos(x) = -frac{1}{2} $ on the unit circle

Answer 1

Abigail Nelson

Samuel Scott

To find the values of $\cos(x) = -\frac{1}{2}$ on the unit circle, we start by considering the unit circle where $\cos(\theta)$ is the x-coordinate of the point corresponding to the angle $\theta$:

\n

$ \cos(x) = -\frac{1}{2} $

\n

We know from trigonometric identities and the unit circle that:

\n

$ \cos(120^\circ) = \cos\left( \frac{2\pi}{3} \right) = -\frac{1}{2} $

\n

$ \cos(240^\circ) = \cos\left( \frac{4\pi}{3} \right) = -\frac{1}{2} $

\n

Therefore, the solutions in degrees are $120^\circ$ and $240^\circ$, and in radians they are:

\n

$ x = \frac{2\pi}{3} + 2k\pi $

\n

$ x = \frac{4\pi}{3} + 2k\pi \quad \text{where } k \in \mathbb{Z} $

Answer 2

Alex Thompson

Henry Green

To find the values where $cos(x) = -frac{1}{2}$ on the unit circle, use the fact that $cos( heta)$ represents the x-coordinate:

$cos(x) = -frac{1}{2}$

From the unit circle, we know:

$cosleft(frac{2pi}{3}
ight) = -frac{1}{2}$

$cosleft(frac{4pi}{3}
ight) = -frac{1}{2}$

Thus, the solutions are:

$x = frac{2pi}{3} + 2kpi$

$x = frac{4pi}{3} + 2kpi$

where $k$ is any integer.

Answer 3

Amelia Mitchell

Mia Harris

To find all $x$ such that $cos(x) = -frac{1}{2}$ on the unit circle, we use:

$cos(x) = -frac{1}{2}$

The solutions are:

$x = frac{2pi}{3} + 2kpi$

$x = frac{4pi}{3} + 2kpi$

where $k in mathbb{Z}$.