1. **State the problem:** We want to evaluate the double integral $$\iint_R \frac{-y}{x^2 y^2 + 1} \, dA$$ where the region $$R$$ is the unit square defined by $$0 \leq x \leq 1$$ and $$0 \leq y \leq 1$$.
2. **Set up the integral:** Since $$R$$ is a rectangle, we can write the double integral as an iterated integral:
$$\int_0^1 \int_0^1 \frac{-y}{x^2 y^2 + 1} \, dy \, dx$$.
3. **Integrate with respect to $$y$$ first:** Fix $$x$$ and consider
$$I(x) = \int_0^1 \frac{-y}{x^2 y^2 + 1} \, dy$$.
4. **Use substitution:** Let $$u = x^2 y^2 + 1$$, then
$$du = 2 x^2 y \, dy \implies y \, dy = \frac{du}{2 x^2}$$.
Rewrite the integral:
$$I(x) = - \int_0^1 \frac{y}{x^2 y^2 + 1} \, dy = - \int_{u=1}^{u=x^2 + 1} \frac{1}{u} \cdot \frac{du}{2 x^2} = - \frac{1}{2 x^2} \int_1^{x^2 + 1} \frac{1}{u} \, du$$.
5. **Integrate:**
$$I(x) = - \frac{1}{2 x^2} [\ln(u)]_1^{x^2 + 1} = - \frac{1}{2 x^2} \ln(x^2 + 1)$$.
6. **Now integrate with respect to $$x$$:**
$$\int_0^1 I(x) \, dx = - \frac{1}{2} \int_0^1 \frac{\ln(x^2 + 1)}{x^2} \, dx$$.
7. **Evaluate the integral $$J = \int_0^1 \frac{\ln(x^2 + 1)}{x^2} \, dx$$:**
This integral is improper at $$x=0$$ because of $$\frac{1}{x^2}$$, but the logarithm behaves well. We use integration by parts:
Let $$u = \ln(x^2 + 1)$$, $$dv = \frac{1}{x^2} dx$$.
Then $$du = \frac{2x}{x^2 + 1} dx$$, and $$v = -\frac{1}{x}$$.
Integration by parts gives:
$$J = uv \bigg|_0^1 - \int_0^1 v \, du = \left[-\frac{\ln(x^2 + 1)}{x}\right]_0^1 + \int_0^1 \frac{1}{x} \cdot \frac{2x}{x^2 + 1} dx = -\ln(2) + \lim_{x \to 0} \frac{\ln(x^2 + 1)}{x} + 2 \int_0^1 \frac{1}{x^2 + 1} dx$$.
The limit $$\lim_{x \to 0} \frac{\ln(x^2 + 1)}{x} = 0$$ by L'Hôpital's rule.
The remaining integral is:
$$2 \int_0^1 \frac{1}{x^2 + 1} dx = 2 [\arctan(x)]_0^1 = 2 \cdot \frac{\pi}{4} = \frac{\pi}{2}$$.
So,
$$J = -\ln(2) + \frac{\pi}{2}$$.
8. **Substitute back:**
$$\int_0^1 I(x) dx = - \frac{1}{2} J = - \frac{1}{2} \left(-\ln(2) + \frac{\pi}{2}\right) = \frac{1}{2} \ln(2) - \frac{\pi}{4}$$.
**Final answer:**
$$\boxed{\frac{1}{2} \ln(2) - \frac{\pi}{4}}$$
Double Integral 47D4Af
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