1. **Problem statement:**
Given that $f$ is an odd function, and that $$\int_0^4 f(|x|) \, dx = 1.6,$$ we need to find:
(i) $$\int_{-4}^0 f(x) \, dx$$
(ii) $$\int_{-4}^4 (f(|x|) + f(x)) \, dx$$
2. **Recall properties of odd functions:**
- A function $f$ is odd if $$f(-x) = -f(x)$$ for all $x$.
- For odd functions, $$\int_{-a}^a f(x) \, dx = 0$$ for any $a$.
3. **Evaluate (i) $$\int_{-4}^0 f(x) \, dx$$:**
Since $f$ is odd,
$$\int_{-4}^0 f(x) \, dx = -\int_0^4 f(x) \, dx$$
But note that $$f(|x|) = f(x)$$ for $x \geq 0$ because $|x|=x$ when $x \geq 0$.
Therefore,
$$\int_0^4 f(|x|) \, dx = \int_0^4 f(x) \, dx = 1.6$$
Hence,
$$\int_{-4}^0 f(x) \, dx = -1.6$$
4. **Evaluate (ii) $$\int_{-4}^4 (f(|x|) + f(x)) \, dx$$:**
Split the integral:
$$\int_{-4}^4 f(|x|) \, dx + \int_{-4}^4 f(x) \, dx$$
- For the first integral, since $f(|x|)$ is an even function (because $|x|$ is even),
$$\int_{-4}^4 f(|x|) \, dx = 2 \int_0^4 f(|x|) \, dx = 2 \times 1.6 = 3.2$$
- For the second integral, since $f$ is odd,
$$\int_{-4}^4 f(x) \, dx = 0$$
Therefore,
$$\int_{-4}^4 (f(|x|) + f(x)) \, dx = 3.2 + 0 = 3.2$$
**Final answers:**
(i) $$\int_{-4}^0 f(x) \, dx = -1.6$$
(ii) $$\int_{-4}^4 (f(|x|) + f(x)) \, dx = 3.2$$
Odd Function Integrals 70A2B9
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