1. We are asked to evaluate the definite integral $$\int_1^{10} \frac{2624}{x^2 + x + 1} \, dx$$.
2. The integral involves a rational function with a quadratic denominator. To solve it, we first complete the square in the denominator:
$$x^2 + x + 1 = \left(x + \frac{1}{2}\right)^2 + \frac{3}{4}$$
3. Rewrite the integral using this:
$$\int_1^{10} \frac{2624}{\left(x + \frac{1}{2}\right)^2 + \left(\frac{\sqrt{3}}{2}\right)^2} \, dx$$
4. Use the substitution:
$$u = x + \frac{1}{2} \implies du = dx$$
5. Change the limits accordingly:
When $x=1$, $u=1 + \frac{1}{2} = \frac{3}{2}$
When $x=10$, $u=10 + \frac{1}{2} = \frac{21}{2}$
6. The integral becomes:
$$\int_{\frac{3}{2}}^{\frac{21}{2}} \frac{2624}{u^2 + \left(\frac{\sqrt{3}}{2}\right)^2} \, du$$
7. Recall the formula for integrals of the form:
$$\int \frac{1}{u^2 + a^2} du = \frac{1}{a} \arctan\left(\frac{u}{a}\right) + C$$
8. Here, $a = \frac{\sqrt{3}}{2}$, so:
$$\int \frac{2624}{u^2 + a^2} du = 2624 \times \frac{1}{a} \arctan\left(\frac{u}{a}\right) + C = \frac{2624}{\frac{\sqrt{3}}{2}} \arctan\left(\frac{2u}{\sqrt{3}}\right) + C$$
9. Simplify the coefficient:
$$\frac{2624}{\frac{\sqrt{3}}{2}} = 2624 \times \frac{2}{\sqrt{3}} = \frac{5248}{\sqrt{3}}$$
10. Evaluate the definite integral:
$$\left. \frac{5248}{\sqrt{3}} \arctan\left(\frac{2u}{\sqrt{3}}\right) \right|_{u=\frac{3}{2}}^{u=\frac{21}{2}} = \frac{5248}{\sqrt{3}} \left[ \arctan\left(\frac{2 \times \frac{21}{2}}{\sqrt{3}}\right) - \arctan\left(\frac{2 \times \frac{3}{2}}{\sqrt{3}}\right) \right]$$
11. Simplify inside the arctan:
$$\arctan\left(\frac{21}{\sqrt{3}}\right) - \arctan\left(\frac{3}{\sqrt{3}}\right) = \arctan\left(\frac{21}{\sqrt{3}}\right) - \arctan\left(\sqrt{3}\right)$$
12. Note that $\arctan(\sqrt{3}) = \frac{\pi}{3}$.
13. The value $\arctan\left(\frac{21}{\sqrt{3}}\right)$ is approximately $1.446$ radians.
14. Therefore, the integral evaluates to approximately:
$$\frac{5248}{\sqrt{3}} (1.446 - 1.047) = \frac{5248}{\sqrt{3}} \times 0.399 \approx 5248 \times 0.230 = 1207.04$$
15. Final answer:
$$\boxed{\int_1^{10} \frac{2624}{x^2 + x + 1} \, dx \approx 1207.04}$$
Definite Integral E81B67
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