Solutions To Selected Problems

Chapter 8

Exercises 8.1

  1. 1.

    T

  2. 3.

    sinx-xcosx+C

  3. 5.

    -x2cosx+2xsinx+2cosx+C

  4. 7.

    1/2ex2+C

  5. 9.

    -12xe-2x-e-2x4+C

  6. 11.

    1/5e2x(sinx+2cosx)+C

  7. 13.

    110e5x(sin(5x)+cos(5x))+C

  8. 15.

    1-x2+xsin-1(x)+C

  9. 17.

    12x2tan-1(x)-x2+12tan-1(x)+C

  10. 19.

    12x2ln|x|-x24+C

  11. 21.

    -x24+12x2ln|x-1|-x2-12ln|x-1|+C

  12. 23.

    13x3ln|x|-x39+C

  13. 25.

    2x+x(ln|x+1|)2+(ln|x+1|)2-2xln|x+1|-2ln|x+1|+2+C

  14. 27.

    ln|sinx|-xcotx+C

  15. 29.

    13(x2-2)3/2+C

  16. 31.

    xsecx-ln|secx+tanx|+C

  17. 33.

    xsinhx-coshx+C

  18. 35.

    xsinh-1x-x2+1+C

  19. 37.

    1/2x(sin(lnx)-cos(lnx))+C

  20. 39.

    12xln|x|-x2+C

  21. 41.

    1/2x2+C

  22. 43.

    π

  23. 45.

    0

  24. 47.

    1/2

  25. 49.

    34e2-54e4

  26. 51.

    15(eπ+e-π)

Exercises 8.2

  1. 1.

    F

  2. 3.

    F

  3. 5.

    14sin4x+C

  4. 7.

    38x+14sin2x+132sin4x+C

  5. 9.

    16cos6x-14cos4x+C

  6. 11.

    12cos2x-ln|cosx|+C

  7. 13.

    (27cos3x-23cosx)cosx+C

  8. 15.

    12(14sin(4x)-110sin(10x))+C

  9. 17.

    12(sin(x)+13sin(3x))+C

  10. 19.

    tanx-x+C

  11. 21.

    tan6(x)6+tan4x4+C

  12. 23.

    sec5(x)5-sec3x3+C

  13. 25.

    13tan3x-tanx+x+C

  14. 27.

    12(secxtanx-ln|secx+tanx|)+C

  15. 29.

    ln|cscx-cotx|+C

  16. 31.

    -12cot2x+ln|cscx|+C

  17. 33.

    25

  18. 35.

    32/315

  19. 37.

    2/3

  20. 39.

    16/15

Exercises 8.3

  1. 1.

    backwards

  2. 3.
    (a) tan2θ+1=sec2θ (b) 9sec2θ.
  3. 5.

    12(xx2+1+ln|x2+1+x|)+C

  4. 7.

    xx2+1/4+14ln|2x2+1/4+2x|+C=12x4x2+1+14ln|4x2+1+2x|+C

  5. 9.

    4(12xx2-1/16-132ln|4x+4x2-1/16|)+C=12x16x2-1-18ln|4x+16x2-1|+C

  6. 11.

    3sin-1(x7)+C (Trig. Subst. is not needed)

  7. 13.

    x2-11-11sec-1(x/11)+C

  8. 15.

    -1x2+9+C (Trig. Subst. is not needed)

  9. 17.

    118x+2x2+4x+13+154tan-1(x+23)+C

  10. 19.

    17(-5-x2x-sin-1(x/5))+C

  11. 21.

    π/2

  12. 23.

    22+2ln(1+2)

  13. 25.

    9sin-1(1/3)+22 Note: the new bounds of integration are sin-1(-1/3)<θ<sin-1(1/3). The final answer comes with recognizing that sin-1(-1/3)=-sin-1(1/3) and that cos(sin-1(1/3))=cos(sin-1(-1/3))=22/3.

Exercises 8.4

  1. 1.

    rational

  2. 3.

    Ax+Bx-3

  3. 5.

    Ax-7+Bx+7

  4. 7.

    3ln|x-2|+4ln|x+5|+C

  5. 9.

    13(ln|x+2|-ln|x-2|)+C

  6. 11.

    -4x+8-3ln|x+8|+C

  7. 13.

    -ln|2x-3|+5ln|x-1|+2ln|x+3|+C

  8. 15.

    x+ln|x-1|-ln|x+2|+C

  9. 17.

    2x+C

  10. 19.

    1x+12ln|x-1x+1|+C

  11. 21.

    ln|3x2+5x-1|+2ln|x+1|+C

  12. 23.

    ln|x|-12ln(x2+1)-tan-1x-12(x2+1)+C

  13. 25.

    12(3ln|x2+2x+17|-4ln|x-7|+tan-1(x+14))+C

  14. 27.

    -14ln(x2+3)+14ln(x2+1)+C=14lnx2+1x2+3+C

  15. 29.

    3(ln|x2-2x+11|+ln|x-9|)+325tan-1(x-110)+C

  16. 31.

    132ln|x-2|-132ln|x+2|-116tan-1(x/2)+C

  17. 33.

    ln(2000/243)2.108

  18. 35.

    -π/4+tan-13-ln(11/9)0.263

Exercises 8.5

  1. 1.

    xsin-1x+1-x2+C

  2. 3.

    18ln|x-2|-9ln|x-1|-5ln|x-3|+C

  3. 5.

    x25x2+25+C

  4. 7.

    2ln|x-1|-ln|x|-1x-1-1(x-1)2+C

  5. 9.

    12ex2(x2-1)+C

  6. 11.

    113e2x(2sin3x-3cos3x)+C

  7. 13.

    -4-x2+C

  8. 15.

    2tan-1x+C

  9. 17.

    127[6xsin3x-(9x2-2)cos3x]+C

  10. 19.

    23(1+ex)3/2+C

  11. 21.

    13tan3x+C

  12. 23.

    -14(8-x3)4/3+C

  13. 25.

    110(3-2x)5/2-12(3-2x)3/2+C

  14. 27.

    25x5/2-83x3/2+6x1/2+C

  15. 29.

    112ln|x+5|-152ln|x+7|+C

  16. 31.

    etanx+C

  17. 33.

    -15cot5x+13cot3x-cotx-x+C

  18. 35.

    13x3-14tanh4x+C

  19. 37.

    3sin-1(x+56)+C

  20. 39.

    13sec3x-secx+C

  21. 41.

    -2sin-1(2x3)-1x9-4x2+C

  22. 43.

    -lnx+4x4+4ln|1-x4|+C

  23. 45.

    -x2(25+x2)+110tan-1(x5)+C

  24. 47.

    14x4-2x2+4ln|x|+C

  25. 49.

    364(2x+3)8/3-920(2x+3)5/3+2716(2x+3)2/3+C

  26. 51.

    -17cos7x+C

  27. 53.

    ln|1+tanθ2|-ln|1-tanθ2|+C

Exercises 8.6

  1. 1.

    The interval of integration is finite, and the integrand is continuous on that interval.

  2. 3.

    converges; could also state 10.

  3. 5.

    p>1

  4. 7.

    e5/2

  5. 9.

    1/3

  6. 11.

    1/ln2

  7. 13.

    diverges

  8. 15.

    1

  9. 17.

    diverges

  10. 19.

    diverges

  11. 21.

    23

  12. 23.

    diverges

  13. 25.

    diverges

  14. 27.

    1

  15. 29.

    0

  16. 31.

    -1/4

  17. 33.

    -1

  18. 35.

    diverges

  19. 37.

    diverges; Limit Comparison Test with 1/x.

  20. 39.

    diverges; Limit Comparison Test with 1/x.

  21. 41.

    converges; Direct Comparison Test with e-x.

  22. 43.

    converges; Direct Comparison Test with 1/(x2-1).

  23. 45.

    converges; Direct Comparison Test with 1/ex.

Exercises 8.7

  1. 1.

    F

  2. 3.

    They are superseded by the Trapezoidal Rule; it takes an equal amount of work and is generally more accurate.

  3. 5.
    (a) 3/4 (b) 2/3 (c) 2/3
  4. 7.
    (a) 14(1+2)π1.896 (b) 16(1+22)π2.005 (c) 2
  5. 9.
    (a) 38.5781 (b) 147/436.75 (c) 147/436.75
  6. 11.
    (a) 0 (b) 0 (c) 0
  7. 13.

    Trapezoidal Rule: 0.9006

    Simpson’s Rule: 0.90452

  8. 15.

    Trapezoidal Rule: 13.9604

    Simpson’s Rule: 13.9066

  9. 17.

    Trapezoidal Rule: 1.1703

    Simpson’s Rule: 1.1873

  10. 19.

    Trapezoidal Rule: 1.0803

    Simpson’s Rule: 1.077

  11. 21.
    (a) n=161 (using max(f′′(x))=1) (b) n=12 (using max(f(4)(x))=1)
  12. 23.
    (a) n=1004 (using max(f′′(x))=39) (b) n=62 (using max(f(4)(x))=800)
  13. 25.
    (a) Area is 30.8667 cm2. (b) Area is 308,667 yd2.
  14. 27.

    Let f(x)=a(x-x1)2+b(x-x1)+c, so that f(x1)=c=y1, f(x1+Δx)=aΔx2+bΔx+c=y2, and f(x1+2Δx)=4aΔx2+2bΔx+c=y3. Therefore, a=y1-2y2+y32(Δx)2 and b=4y2-y3-3y12Δx, and x1x1+2Δxa(x-x1)2+b(x-x1)+cdx=a(2Δx)33+b(2Δx)22+c(2Δx)=4(y1-2y2+y3)Δx3+(4y2-y3-3y1)Δx+2y1Δx=Δx3(4y1-8y2+4y3+12y2-3y3-9y1+6y1)=Δx3(y1+4y2+y3).

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