Cosine Graph B242Ee
1. **State the problem:** We want to graph one period of the function $$y = -3 \cos\left(\frac{1}{2}(x - \frac{\pi}{3})\right) + 1$$ and understand how to move the graph horizontally and vertically.
2. **Identify key parameters:**
- Amplitude: $$3$$ (the coefficient before cosine, absolute value)
- Period: $$\frac{2\pi}{\frac{1}{2}} = 4\pi$$
- Horizontal phase shift: $$\frac{\pi}{3}$$ units to the right (inside the cosine argument)
- Vertical displacement: $$1$$ unit up (added outside cosine)
3. **Explain horizontal shift:**
The expression inside cosine is $$\frac{1}{2}(x - \frac{\pi}{3})$$.
To find the horizontal shift in terms of $$x$$, set the inside equal to zero:
$$\frac{1}{2}(x - \frac{\pi}{3}) = 0 \implies x = \frac{\pi}{3}$$.
This means the entire graph shifts $$\frac{\pi}{3}$$ units to the right.
4. **Explain period and scaling:**
The period of cosine normally is $$2\pi$$.
Because of the factor $$\frac{1}{2}$$ multiplying $$x$$, the period stretches by a factor of $$\frac{1}{\frac{1}{2}} = 2$$, so the new period is $$4\pi$$.
5. **Explain vertical shift:**
The $$+1$$ outside the cosine moves the entire graph up by 1 unit.
6. **Graphing steps:**
- Start by plotting the baseline at $$y=1$$.
- Mark the horizontal axis from $$x=0$$ to $$x=4\pi$$ to cover one full period.
- Shift the graph right by $$\frac{\pi}{3}$$ units.
- The maximum value is $$1 + 3 = 4$$ and minimum is $$1 - 3 = -2$$.
- The cosine wave starts at maximum at $$x=\frac{\pi}{3}$$, goes down to minimum at $$x=\frac{\pi}{3} + 2\pi$$, and back to maximum at $$x=\frac{\pi}{3} + 4\pi$$.
7. **Summary:**
- Move the graph horizontally right by $$\frac{\pi}{3}$$.
- Stretch the period to $$4\pi$$.
- Move the graph vertically up by 1.
- Amplitude controls height from baseline.
This explains how to move the graph horizontally and vertically and how to plot one period of the function.