Practice Problems

Use the integral table for the following problems.

1. $\int \frac{1}{4+x^{2}} \mathrm{dx}$

3. $\int 2 x+\frac{2}{25+x^{2}} d x$

5. $\int \frac{2}{9-x^{2}} d x$

7. $\int \frac{1}{3+x^{2}} \mathrm{dx}$

9. $\int e^{x}+\frac{7}{2+x^{2}} d x$

11. $\int \frac{3}{\sqrt{5-x^{2}}} \mathrm{dx}$

13. $\int \frac{1}{4+25 x^{2}} \mathrm{dx}$

15. $\int \frac{5}{\sqrt{1-4 x^{2}}} d x$

17. $\int \frac{2}{\sqrt{1+9 x^{2}}} \mathrm{dx}$

19. $\int \ln (x+1) \mathrm{dx}$

21. $\int 3 x \cdot \ln \left(5 x^{2}+7\right) \mathrm{dx}$

23. $\int \cos (x) \ln (\sin (x)) \mathrm{dx}$

25. $\int \sqrt{4+x^{2}} d x$

27. $\int \sqrt{16+x^{2}} d x$

29. $\int_{1}^{3} 2 x+\frac{2}{25+x^{2}} \mathrm{dx}$

31. $\int_{-1}^{1} \frac{1}{3+x^{2}} d x$

33. $\int_{1}^{2} \frac{3}{\sqrt{5-x^{2}}} \mathrm{dx}$

35. $\int_{0}^{0.1} \frac{5}{\sqrt{1-4 x^{2}}} d x$

37. $\int_{0}^{6} \ln (x+1) \mathrm{dx}$

39. $\int_{0}^{\pi / 2} \cos (x) \ln (2+\sin (x)) \mathrm{dx}$

41. $\int_{-3}^{3} \sqrt{9+x^{2}} d x$

In problems 43 – 47 , use the recursion formulas in the table

43. $\int \sin ^{3}(x) \mathrm{dx}$

45. $\int \cos ^{5}(x) \mathrm{dx}$

47. $\int x^{2} \cos (x) \mathrm{dx}$

49. Before doing any calculations, predict which do you expect to be larger; the average value of $\sin (x)$ or of $\sin ^{2}(x)$ on the interval $[0, \pi]$? Then calculate each average to see if your prediction was correct.

51. Find the average value of $\mathrm{f}(x)=\ln (x)$ on the interval $1 \leq x \leq C$ when $C=e, 10,100,200$

53. Before doing any calculations, predict which of the following integrals you expect to be the largest?

(a) $\int_{1}^{2} e^{x} d x$ (b) $\int_{1}^{2} x \mathrm{e}^{x} \mathrm{dx}$ (c) $\int_{1}^{2} x^{2} e^{x} d x$ Then calculate the value of each integral.

55. Evaluate $\int_{0}^{\mathrm{C}} \frac{2}{1+x^{2}} \mathrm{dx}$ fo $\mathrm{C}=1,10,20, \text { and } 30$. Before doing the calculation, estimate the value of the integral when $C = 40$.

Source: Dale Hoffman, https://s3.amazonaws.com/saylordotorg-resources/wwwresources/site/wp-content/uploads/2012/12/MA005-5.9-Using-Tables-to-Find-Antiderivatives.pdf
This work is licensed under a Creative Commons Attribution 3.0 License.

1. Table #35, $a=2: \quad \frac{1}{2} \arctan \left(\frac{x}{2}\right)+C$

3. Table #35, $\mathrm{a}=5: \quad \mathrm{x}^{2}+\frac{2}{5} \arctan \left(\frac{\mathrm{x}}{5}\right)+\mathrm{C}$

5. Table #37, $\mathrm{a}=3: \quad\left(\frac{1}{3}\right) \ln \mid \frac{x+3}{x-3} 1+C$

7. Table #35, $\mathrm{a}=\sqrt{3}: \frac{1}{\sqrt{3}} \arctan \left(\frac{\mathrm{x}}{\sqrt{3}}\right)+\mathrm{C}$

9. Table #35, $a=\sqrt{2}: e^{x}+\frac{7}{\sqrt{2}} \arctan \left(\frac{x}{\sqrt{2}}\right)+C$

11. Table #34, $a=\sqrt{5}: 3 \cdot \arcsin \left(\frac{x}{\sqrt{5}}\right)+C$

13. Table #35, $\mathrm{a}=\frac{2}{5}: \frac{1}{10} \arctan \left(\frac{5}{2} \mathrm{x}\right)+\mathrm{C}$

15. First substitute $\mathbf{u}=2 \mathrm{x}, \mathrm{d} \mathrm{u}=2 \mathrm{dx}$. Then use Table #34 with $\mathrm{a}=1: \frac{5}{2} \cdot \arcsin (\mathrm{u})+\mathrm{C}=\frac{5}{2} \cdot \arcsin (2 \mathrm{x})+\mathrm{C}$

17. Table #43 and substitution $\mathrm{u}=3 \mathrm{x}: \frac{2}{3} \ln \mid 3 \mathrm{x}+\sqrt{1+9 \mathrm{x}^{2}} \mathrm{I}+\mathrm{C}$.

19. Table #38 and substitution $\mathrm{u}=\mathrm{x}+1:(\mathrm{x}+1) \cdot \ln \mid \mathrm{x}+11-(\mathrm{x}+1)+\mathrm{C} \text { or }(\mathrm{x}+1) \cdot \ln \mid \mathrm{x}+1 \mathrm{l}-\mathrm{x}+\mathrm{C}_{2}$

21. Table #38 and substitution $u=5 x^{2}+7: \frac{3}{10}\left\{\left(5 x^{2}+7\right) \cdot \ln 15 x^{2}+7 \mid-\left(5 x^{2}+7\right)\right\}+C$

23. Table #38 and substitution $\mathrm{u}=\sin (\mathrm{x}): \sin (\mathrm{x}) \cdot \ln |\sin (\mathrm{x})|-\sin (\mathrm{x})+\mathrm{C}$

25. Table #44, $\mathrm{a}=2: \frac{\mathrm{x}}{2} \sqrt{\mathrm{x}^{2}+4}+\frac{1}{2}(4) \cdot \ln \mid \mathrm{x}+\sqrt{\mathrm{x}^{2}+4} \mathrm{I}+\mathrm{C}$

27. Table #44, $a=4: \frac{x}{2} \sqrt{x^{2}+16}+\frac{1}{2}(16) \cdot \ln \mid x+\sqrt{x^{2}+16} 1+C$

29. Table #35, $\mathrm{a}=5: \mathrm{x}^{2}+\left.\frac{2}{5} \arctan \left(\frac{\mathrm{x}}{5}\right)\right|_{1} ^{3}=8+\frac{2}{5}\left\{\arctan \left(\frac{3}{5}\right)-\operatorname{acrtan}\left(\frac{1}{5}\right)\right\}$

31. Table #35, $\mathrm{a}=\sqrt{3}:\left.\frac{1}{\sqrt{3}} \operatorname{acrtan}\left(\frac{\mathrm{x}}{\sqrt{3}}\right)\right|_{-1} ^{1}=\frac{1}{\sqrt{3}}\left\{\arctan \left(\frac{1}{\sqrt{3}}\right)-\arctan \left(\frac{-1}{\sqrt{3}}\right)\right\}$

33. Table #34, $\mathrm{a}=\sqrt{5}:\left.3 \arcsin \left(\frac{\mathrm{x}}{\sqrt{5}}\right)\right|_{1} ^{2}=3 \cdot\left\{\operatorname { a r c s i n } \left(\frac{2}{\sqrt{5}}-\arcsin \left(\frac{1}{\sqrt{5}}\right\}\right.\right.$

35. Table #34, $a=1 / 2:\left.\frac{5}{2} \arcsin \left(\frac{x}{1 / 2}\right)\right|_{0} ^{0.1}=\frac{5}{2} \arcsin (0.2)$

37. $7 \cdot \ln (7)-6$

39. $3 \cdot \ln (3)-2 \cdot \ln (2)-1$

41. $3 \sqrt{18}+\frac{9}{2} \cdot \ln \left(\frac{3+\sqrt{18}}{-3+\sqrt{18}}\right)$

43. Table #19a: $\frac{-\sin ^{2}(x) \cdot \cos (x)}{3}-\frac{2}{3} \cos (x)+C$

45. Table #20: $\frac{\cos ^{4}(\mathrm{x}) \cdot \sin (\mathrm{x})}{5}+\frac{4}{5}$ { answer to number 44 }

47. Table #29: $x^{2} \cdot \sin (x)+2 x^{*} \cos (x)-2 \cdot \sin (x)+C$

49. Average of $\sin (x)$ on $[0, \pi]$ is $\frac{2}{\pi}$. Average of $\sin ^{2}(x)$ on $[0, \pi]$ is $\frac{1}{2} \cdot \frac{2}{\pi}>\frac{1}{2}$

51. Using results from #50: (a) $\frac{1}{\mathrm{e}-1}$                                           (b) $\frac{1}{9}\{10 \cdot \ln (10)-9\} \approx \frac{14.03}{9} \approx 1.56$ 

(c) $\frac{1}{99}\{100 \cdot \ln (100)-99\} \approx 361.52 / 99 \approx 3.65$                (d) $\frac{1}{199}\{200 \cdot \ln (200)-199\} \approx 860.66 / 199=4.32$

53. (c) is largest.

55. approximately (a) $1.57$ (b) $2.94$ (c) $3.04$ (d) $3.07$ (e) $3.09$