Exercise 8.8:

In Exercises 31 – 32, approximate the value of the given definite integral by using the first ϰ nonzero terms of the integrand’s Taylor series.

  1. \[ A = \int_{0}^{\sqrt{x}}sin(x^2)dx \]

  2. \[ A = \int_{0}^{\frac{x^2}{4}}cos(\sqrt{x})dx \]

To approximate the value of the given definite integrals using the first κ nonzero terms of the integrand’s Taylor series,

we will find the Taylor series expansions of the integrands and then integrate each term separately.

31.Solution:

\[ A = \int_{0}^{\sqrt{x}}sin(x^2)dx \]

The Taylor series expansion of sin(x^2) around x=0 is:

\[sin(x^2) = x^2 - \frac{x^6}{3!} + \frac{x^{10}}{5!}\] ⁡ Now, integrate each term of the series separately:

\[A \approx \int_{0}^{\sqrt{x}}(x^2 - \frac{x^6}{3!} + \frac{x^{10}}{5!}-...)dx\]

Integrate term by term and sum them up to get the final approximation.

32.Solution:

\[ A = \int_{0}^{\frac{x^2}{4}}cos(\sqrt{x})dx \]

The Taylor series expansion of cos(sqrt(x)) around x=0 is:

\[cos (\sqrt{x})= 1-\frac{x}{2} + \frac{x^2}{4!}-...\] ⁡ Next, we integrate each term of the series separately:

\[A \approx \int_{0}^\frac{x^2}{4}(1-\frac{x}{2} + \frac{x^2}{4!}-...)dx\]

Integrate term by term and sum them up to get the final approximation.