Sin Cos Intersections 7Bccf4
1. **State the problem:**
We need to sketch the graphs of $y = \sin 2x$ and $y = 1 + \cos 2x$ for $0^\circ \leq x \leq 360^\circ$ and find the number of solutions to the equation $\sin 2x = 1 + \cos 2x$ in this interval.
2. **Recall the functions and their properties:**
- $y = \sin 2x$ is a sine wave with frequency doubled, so it completes two full cycles from $0^\circ$ to $360^\circ$.
- $y = 1 + \cos 2x$ is a cosine wave with frequency doubled and shifted up by 1 unit.
3. **Sketching the graphs:**
- $\sin 2x$ oscillates between $-1$ and $1$ with zeros at $x=0^\circ, 90^\circ, 180^\circ, 270^\circ, 360^\circ$.
- $1 + \cos 2x$ oscillates between $0$ and $2$ with maxima at $x=0^\circ, 180^\circ, 360^\circ$ and minima at $x=90^\circ, 270^\circ$.
4. **Find the number of solutions to $\sin 2x = 1 + \cos 2x$:**
Rewrite the equation:
$$\sin 2x = 1 + \cos 2x$$
Use the identity $\sin 2x - \cos 2x = 1$.
5. **Express $\sin 2x - \cos 2x$ as a single sine function:**
Recall that:
$$\sin A - \cos A = \sqrt{2} \sin \left(A - 45^\circ\right)$$
So,
$$\sin 2x - \cos 2x = \sqrt{2} \sin \left(2x - 45^\circ\right)$$
6. **Set the equation:**
$$\sqrt{2} \sin \left(2x - 45^\circ\right) = 1$$
Divide both sides by $\sqrt{2}$:
$$\sin \left(2x - 45^\circ\right) = \frac{1}{\sqrt{2}} = \sin 45^\circ$$
7. **Solve for $2x - 45^\circ$:**
The general solutions for $\sin \theta = \sin \alpha$ are:
$$\theta = \alpha + 360^\circ k \quad \text{or} \quad \theta = 180^\circ - \alpha + 360^\circ k$$
where $k$ is any integer.
So,
$$2x - 45^\circ = 45^\circ + 360^\circ k \quad \text{or} \quad 2x - 45^\circ = 135^\circ + 360^\circ k$$
8. **Solve for $x$:**
For the first case:
$$2x = 90^\circ + 360^\circ k \Rightarrow x = 45^\circ + 180^\circ k$$
For the second case:
$$2x = 180^\circ + 360^\circ k \Rightarrow x = 90^\circ + 180^\circ k$$
9. **Find all solutions in $0^\circ \leq x \leq 360^\circ$:**
For $x = 45^\circ + 180^\circ k$:
- $k=0 \Rightarrow x=45^\circ$
- $k=1 \Rightarrow x=225^\circ$
- $k=2 \Rightarrow x=405^\circ$ (outside range)
For $x = 90^\circ + 180^\circ k$:
- $k=0 \Rightarrow x=90^\circ$
- $k=1 \Rightarrow x=270^\circ$
- $k=2 \Rightarrow x=450^\circ$ (outside range)
10. **Count the solutions:**
The solutions within the interval are:
$$45^\circ, 90^\circ, 225^\circ, 270^\circ$$
There are 4 solutions.
**Final answer:**
- The graphs of $y=\sin 2x$ and $y=1+\cos 2x$ intersect 4 times in $0^\circ \leq x \leq 360^\circ$.