Cosine Double Angle
1. **State the problem:**
We need to find all angles $x$ between 0 and 360 degrees such that $$\cos(2x) = \frac{\sqrt{3}}{2}.$$
2. **Recall the cosine values:**
The value $\frac{\sqrt{3}}{2}$ corresponds to cosine values at angles 30° and 330° (since cosine is positive in the first and fourth quadrants).
3. **Set up the general solutions for $2x$:**
Since $$\cos(\theta) = \frac{\sqrt{3}}{2}$$ at $$\theta = 30^\circ + 360^\circ k$$ or $$\theta = 330^\circ + 360^\circ k,$$ where $k$ is any integer.
Thus,
$$2x = 30^\circ + 360^\circ k$$ or $$2x = 330^\circ + 360^\circ k.$$
4. **Solve for $x$:**
Divide both sides of each equation by 2:
$$x = 15^\circ + 180^\circ k$$ or $$x = 165^\circ + 180^\circ k.$$
5. **Find values of $x$ between 0° and 360°:**
- For $$x = 15^\circ + 180^\circ k$$:
- If $k=0$, $x = 15^\circ$
- If $k=1$, $x = 195^\circ$
- If $k=2$, $x = 375^\circ$ (outside range)
- If $k=-1$, $x = -165^\circ$ (outside range)
So possible $x$ are $15^\circ$ and $195^\circ$.
- For $$x = 165^\circ + 180^\circ k$$:
- If $k=0$, $x = 165^\circ$
- If $k=1$, $x = 345^\circ$
- If $k=2$, $x = 525^\circ$ (outside range)
- If $k=-1$, $x = -15^\circ$ (outside range)
So possible $x$ are $165^\circ$ and $345^\circ$.
6. **Final solution:**
All possible values for $x$ in $[0^\circ, 360^\circ]$ are:
$$\boxed{15^\circ, 165^\circ, 195^\circ, 345^\circ}.$$