Chapter 8 - Techniques of Integration - 8.4 Integrals Involving Hyperbolic and Inverse Hyperbolic Functions - Exercises - Page 415: 28

$$\operatorname{sech}^{-1}(0.2)-\operatorname{sech}^{-1}(0.8)$$

\begin{aligned} \int_{0.2}^{0.8} \frac{1}{x \sqrt{1-x^{2}}} d x &=\left[-\operatorname{sech}^{-1} x\right]_{0.2}^{0.8} \\ &=-\operatorname{sech}^{-1}(0.8)-\left[-\operatorname{sech}^{-1}(0.2)\right] \\ &=\operatorname{sech}^{-1}(0.2)-\operatorname{sech}^{-1}(0.8) \end{aligned}