Solutions To Selected Problems

Chapter 7

Exercises 7.1

  1. 1.

    F

  2. 3.

    The point (10,1) lies on the graph of y=f-1(x) (assuming f is invertible).

  3. 5.
    -9-8-7-6-5-4-3-2-1123456789-8-7-6-5-4-3-2-112345678f(x)xy
  4. 7.

    Compose f(g(x)) and g(f(x)) to confirm that each equals x.

  5. 9.

    Compose f(g(x)) and g(f(x)) to confirm that each equals x.

  6. 11.

    [-4,0] or [0,4]

  7. 13.

    (-,3] or [3,)

  8. 15.

    f-1(x)=2x+1x-1

  9. 17.

    f-1(x)=ln(x+2)-3

  10. 19.

    0

  11. 21.

    -1/5

  12. 23.

    1/2

  13. 25.

    7/58

  14. 27.

    3π/4

  15. 29.

    x/2

  16. 31.

    x/x2+25

  17. 33.
  18. 35.
  19. 37.

    2π/33

Exercises 7.2

  1. 1.

    The point (10,1) lies on the graph of y=f-1(x) (assuming f is invertible) and (f-1)(10)=1/5.

  2. 3.

    (f-1)(20)=1f(2)=1/5

  3. 5.

    (f-1)(3/2)=1f(π/6)=1

  4. 7.

    (f-1)(1/2)=1f(1)=-2

  5. 9.

    h(t)=21-4t2

  6. 11.

    g(x)=21+4x2

  7. 13.

    g(t)=cos-1(t)cos(t)-sin(t)1-t2

  8. 15.

    h(x)=sin-1x+cos-1x1-x2(cos-1x)2

  9. 17.

    f(x)=-11-x2

  10. 19.
    (a) f(x)=x, so f(x)=1 (b) f(x)=cos(sin-1x)11-x2=1.
  11. 21.
    (a) f(x)=1-x2, so f(x)=-x1-x2 (b) f(x)=cos(cos-1x)(11-x2)=-x1-x2
  12. 23.

    y=2(x-2/2)+π/4

  13. 25.

    -π/6

  14. 27.

    12(sin-1r)2+C

  15. 29.

    sin-1(et/10)+C

  16. 31.

    919.54 feet

Exercises 7.3

  1. 1.

    (-,)

  2. 3.

    (-,0)(0,)

  3. 5.

    f(t)=3t2et3-1

  4. 7.

    f(x)=1-xln5lnxx5xln5

  5. 9.

    f(x)=1

  6. 11.

    h(r)=3rln31+32r

  7. 13.

    24ln5

  8. 15.

    3x2-12ln3+C

  9. 17.

    12sin2(ex)+C

  10. 19.

    ln245ln3-1

  11. 21.

    12ln2(x)+C

  12. 23.

    16ln2(x3)+C

  13. 25.

    n=-3,2

  14. 27.

    y=(1+x)1/x(1x(x+1)-ln(1+x)x2)

    Tangent line: y=(1-2ln2)(x-1)+2

  15. 29.

    y=xxx+1(lnx+1-1x+1)

    Tangent line: y=(1/4)(x-1)+1/2

  16. 31.

    y=x+1x+2(1x+1-1x+2)

    Tangent line: y=1/9(x-1)+2/3

  17. 33.

    y=xex-1ex(1+xlnx)

    Tangent line: y=ex-e+1

  18. 35.

    r=(ln2)/5730; 5730ln10/ln219034.65 years

Exercises 7.4

  1. 1.

    Because coshx is always positive.

  2. 3.

    cosht=13/12, etc.

  3. 5.

    coth2x-csch2x=(ex+e-xex-e-x)2-(2ex-e-x)2=(e2x+2+e-2x)-(4)e2x-2+e-2x=e2x-2+e-2xe2x-2+e-2x=1

  4. 7.

    cosh2x=(ex+e-x2)2=e2x+2+e-2x4=12(e2x+e-2x)+22=12(e2x+e-2x2+1)=cosh2x+12.

  5. 9.

    ddx[sechx]=ddx[2ex+e-x]=-2(ex-e-x)(ex+e-x)2=-2(ex-e-x)(ex+e-x)(ex+e-x)=-2ex+e-xex-e-xex+e-x=-sechxtanhx

  6. 11.
    tanhxdx=sinhxcoshxdx Let u=coshx; du=(sinhx)dx =1udu=ln|u|+C=ln(coshx)+C.
  7. 13.

    2cosh2x

  8. 15.

    2xsech2(x2)

  9. 17.

    sinh2x+cosh2x

  10. 19.

    -2x(x2)1-x4

  11. 21.

    4x4x4-1

  12. 23.

    -cscx

  13. 25.

    y=x

  14. 27.

    y=925(x+ln3)-45

  15. 29.

    y=x

  16. 31.

    12ln(cosh(2x))+C

  17. 33.

    12sinh2x+C or 1/2cosh2x+C

  18. 35.

    cosh-1(x2/2)+C=ln(x2+x4-4)+C

  19. 37.

    tan-1(ex)+C

  20. 39.

    0

  21. 41.

    Using rule #33: A=0sinhθ1+y2-ycothθdy=θ2.

Exercises 7.5

  1. 1.

    0/0,/,0,-,00,1,0

  2. 3.

    F

  3. 5.

    derivatives; limits

  4. 7.

    Answers will vary.

  5. 9.

    3

  6. 11.

    -1

  7. 13.

    5

  8. 15.

    a/b

  9. 17.

    1/2

  10. 19.

    0

  11. 21.

  12. 23.

    0

  13. 25.

    -2

  14. 27.

    0

  15. 29.

    0

  16. 31.

  17. 33.

  18. 35.

    0

  19. 37.

    1

  20. 39.

    1

  21. 41.

    1

  22. 43.

    1

  23. 45.

    1

  24. 47.

    2

  25. 49.

    -

  26. 51.

    0

  27. 53.

    53

  28. 55.

    Use technology to verify sketch.

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