Home > CALC > Chapter 10 > Lesson 10.3.1 > Problem10-118

10-118.

Examine the integrals below. Consider the multiple tools available for integrating and use the best strategy. After evaluating each integral, write a short description of your method.

1. $\int \operatorname { sec } ^ { 4 } ( x ) \operatorname { tan } ^ { 3 } ( x ) d x$

Rewrite the integrand in terms of sine and cosine and use the Pythagorean Identity.

$=\int\frac{(1-\cos^2(x))\sin(x)}{\cos^7(x)}dx$

Let $u =\operatorname{cos}(x)$.

1. $\int x \operatorname { tan } ^ { - 1 } ( x ) d x$

Use integration by parts: Let $f =\operatorname{tan}^{–1}(x)$ and $dg = x dx$

$\int x\tan^{-1}(x)dx=\frac{1}{2}x^2\tan^{-1}(x)-\frac{1}{2}\int \frac{x^2}{1+x^2}dx$

Use polynomial division:
$=\frac{1}{2}x^2\tan^{-1}(x)-\frac{1}{2}\int \Big(1-\frac{1}{1+x^2}\Big)dx$

1. $\int \frac { \operatorname { ln } x } { x } d x$

Use substitution: Let $u =\operatorname{ln}(x)$

1. $\int \frac { \operatorname { cos } \sqrt { x } } { \sqrt { x } } d x$

Use substitution:
$\text{Let }u=\sqrt{x}$