Integrals Semicycles Caef1E
1. **Problem Statement:** Calculate the definite integrals of the function $f(x)$ whose graph consists of semicircles below and above the x-axis on given intervals.
2. **Understanding the graph:**
- From $x=0$ to $x=2$, $f(x)$ is a semicircle below the x-axis.
- From $x=2$ to $x=6$, $f(x)$ is a semicircle above the x-axis.
- The curve intersects the x-axis at $x=0, 2, 4, 6$.
3. **Formula for area of a semicircle:**
$$\text{Area} = \frac{1}{2} \pi r^2$$
where $r$ is the radius of the semicircle.
4. **Calculate radii:**
- For $0 \leq x \leq 2$, radius $r=2$ (since the semicircle spans 2 units).
- For $2 \leq x \leq 4$, radius $r=2$.
- For $4 \leq x \leq 6$, radius $r=2$.
5. **Calculate each integral:**
A. $\int_0^2 f(x) \, dx$ is the area of the semicircle below x-axis, so integral is negative:
$$\int_0^2 f(x) \, dx = -\frac{1}{2} \pi (2)^2 = -2\pi \approx -6.28$$
B. $\int_1^4 f(x) \, dx$ covers part of the semicircle below x-axis from 1 to 2 and the semicircle above x-axis from 2 to 4.
- Area from 1 to 2 (half of semicircle below x-axis): half of $-2\pi$ is $-\pi \approx -3.14$
- Area from 2 to 4 (full semicircle above x-axis): $+2\pi \approx +6.28$
- Total:
$$-3.14 + 6.28 = 3.14$$
C. $\int_1^4 |f(x)| \, dx$ is the sum of absolute areas:
$$3.14 + 6.28 = 9.42$$
D. $\int_4^2 f(x) \, dx = -\int_2^4 f(x) \, dx = -2\pi \approx -6.28$$
E. $\int_4^4 f(x) \, dx = 0$ (integral over zero width interval).
**Final answers rounded to 2 decimals:**
A. $-6.28$
B. $3.14$
C. $9.42$
D. $-6.28$
E. $0.00$