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Calculus 3 Review 2

    This topic is a collection of problems and concepts that might help someone understand their working knowledge of Calculus 3.

Show all work and justify each step.

(1) Find parametric equations for the tangent line to the graph of  

calculus 3 review 2 _gr_1.gif]

at the highest point on the graph.

    Solution. We want calculus 3 review 2 _gr_2.gif] where calculus 3 review 2 _gr_3.gif] and since

calculus 3 review 2 _gr_4.gif]

we find that calculus 3 review 2 _gr_5.gif] Further,
    
calculus 3 review 2 _gr_6.gif]
and so

calculus 3 review 2 _gr_7.gif]

Also, calculus 3 review 2 _gr_8.gif] and therefore, the parametric equations for the tangent line at the highest point are

calculus 3 review 2 _gr_9.gif]

calculus 3 review 2 _gr_10.gif]

calculus 3 review 2 _gr_11.gif]

calculus 3 review 2 _gr_12.gif]

(2) Find the length of the graph of the vector function

calculus 3 review 2 _gr_13.gif]

from calculus 3 review 2 _gr_14.gif] to calculus 3 review 2 _gr_15.gif]

    Solution. We determine calculus 3 review 2 _gr_16.gif] and so

calculus 3 review 2 _gr_17.gif]

Therefore, calculus 3 review 2 _gr_18.gif] which is the desired length. calculus 3 review 2 _gr_19.gif]
    
(3) If calculus 3 review 2 _gr_20.gif] show that calculus 3 review 2 _gr_21.gif]

    Solution. Let calculus 3 review 2 _gr_22.gif] and calculus 3 review 2 _gr_23.gif] so calculus 3 review 2 _gr_24.gif] then

calculus 3 review 2 _gr_25.gif]

calculus 3 review 2 _gr_26.gif]

Therefore,

calculus 3 review 2 _gr_27.gif]

calculus 3 review 2 _gr_28.gif]
    
(4) Suppose the system

calculus 3 review 2 _gr_29.gif]

can be solved for calculus 3 review 2 _gr_30.gif] and calculus 3 review 2 _gr_31.gif] in terms of calculus 3 review 2 _gr_32.gif] and calculus 3 review 2 _gr_33.gif] so that calculus 3 review 2 _gr_34.gif] and calculus 3 review 2 _gr_35.gif] Use implicit differentiation to find the partial derivatives calculus 3 review 2 _gr_36.gif] and calculus 3 review 2 _gr_37.gif]

    Solution. We use implicit differentiation on

calculus 3 review 2 _gr_38.gif] = 0
to find calculus 3 review 2 _gr_39.gif] We have,

calculus 3 review 2 _gr_40.gif]

and so

calculus 3 review 2 _gr_41.gif]

Also,     
    
calculus 3 review 2 _gr_42.gif]
    
and so

calculus 3 review 2 _gr_43.gif]

So we can solve the system

calculus 3 review 2 _gr_44.gif]

to obtain

calculus 3 review 2 _gr_45.gif]

calculus 3 review 2 _gr_46.gif]

calculus 3 review 2 _gr_47.gif]

(5) Find the direction from calculus 3 review 2 _gr_48.gif] in which the function

calculus 3 review 2 _gr_49.gif]

increases most rapidly and compute the magnitude of the greatest rate of increase.
    
    Solution. We compute the gradient:

calculus 3 review 2 _gr_50.gif]

and at calculus 3 review 2 _gr_51.gif] we have,

calculus 3 review 2 _gr_52.gif]

Therefore, calculus 3 review 2 _gr_53.gif] is the magnitude of the greatest rate of increase and occurs in the direction of calculus 3 review 2 _gr_54.gif] calculus 3 review 2 _gr_55.gif]

(6) Find the directional derivative of calculus 3 review 2 _gr_56.gif] at calculus 3 review 2 _gr_57.gif] in the direction toward the origin.

    Solution. We use the unit vector

calculus 3 review 2 _gr_58.gif]

and find

calculus 3 review 2 _gr_59.gif]

to compute

calculus 3 review 2 _gr_60.gif]

calculus 3 review 2 _gr_61.gif]

(7) Find the absolute extrema of calculus 3 review 2 _gr_62.gif]on the closed bounded set calculus 3 review 2 _gr_63.gif] defined by the disk calculus 3 review 2 _gr_64.gif]

    Solution. We find calculus 3 review 2 _gr_65.gif] and calculus 3 review 2 _gr_66.gif] and so calculus 3 review 2 _gr_67.gif] only at calculus 3 review 2 _gr_68.gif] To check the boundary calculus 3 review 2 _gr_69.gif] we let calculus 3 review 2 _gr_70.gif] and calculus 3 review 2 _gr_71.gif] for calculus 3 review 2 _gr_72.gif] Then calculus 3 review 2 _gr_73.gif] and so

calculus 3 review 2 _gr_74.gif]

Thus calculus 3 review 2 _gr_75.gif] when calculus 3 review 2 _gr_76.gif] which yields the points

calculus 3 review 2 _gr_77.gif]

respectively. Therefore, calculus 3 review 2 _gr_78.gif] is a minimum and

calculus 3 review 2 _gr_79.gif]

is the maximum value and

calculus 3 review 2 _gr_80.gif]

does not yield extrema values. calculus 3 review 2 _gr_81.gif]

(8) A wire of length calculus 3 review 2 _gr_82.gif] is cut into three pieces that are bent to form a circle, a square, and an equilateral triangle. How should the cuts be made to minimize the sum of the total area?

    Solution. Let calculus 3 review 2 _gr_83.gif] be the length of each side of the square, calculus 3 review 2 _gr_84.gif] be the length of each side of the triangle, and calculus 3 review 2 _gr_85.gif] the radius of the circle. We wish to optimize calculus 3 review 2 _gr_86.gif] subject to calculus 3 review 2 _gr_87.gif] calculus 3 review 2 _gr_88.gif] calculus 3 review 2 _gr_89.gif] and calculus 3 review 2 _gr_90.gif] Since calculus 3 review 2 _gr_91.gif] we have

calculus 3 review 2 _gr_92.gif]

with

calculus 3 review 2 _gr_93.gif]

calculus 3 review 2 _gr_94.gif]

Then calculus 3 review 2 _gr_95.gif] when simultaneously,

calculus 3 review 2 _gr_96.gif]  

calculus 3 review 2 _gr_97.gif]

We obtain

calculus 3 review 2 _gr_98.gif]

calculus 3 review 2 _gr_99.gif]

Since calculus 3 review 2 _gr_100.gif] and

calculus 3 review 2 _gr_101.gif]

calculus 3 review 2 _gr_102.gif]

(9) Minimize calculus 3 review 2 _gr_103.gif] subject to calculus 3 review 2 _gr_104.gif] and calculus 3 review 2 _gr_105.gif]

    Solution. We set calculus 3 review 2 _gr_106.gif] and calculus 3 review 2 _gr_107.gif] and we use the Lagrange multipliers to set up the system

calculus 3 review 2 _gr_108.gif]

which is
    
calculus 3 review 2 _gr_109.gif]

to find calculus 3 review 2 _gr_110.gif] which leads to calculus 3 review 2 _gr_111.gif] as the minimize subject to calculus 3 review 2 _gr_112.gif] and calculus 3 review 2 _gr_113.gif] calculus 3 review 2 _gr_114.gif]

(10) Find the maximum and minimum values of calculus 3 review 2 _gr_115.gif] on the surface calculus 3 review 2 _gr_116.gif]

    Solution. We set calculus 3 review 2 _gr_117.gif] and we use the Lagrange multiplier calculus 3 review 2 _gr_118.gif] and solve the system
    
calculus 3 review 2 _gr_119.gif]

which is
    
calculus 3 review 2 _gr_120.gif]

to find

calculus 3 review 2 _gr_121.gif]

Therefore,

calculus 3 review 2 _gr_122.gif]  

is the minimum and

calculus 3 review 2 _gr_123.gif]

is the maximum value. calculus 3 review 2 _gr_124.gif]

(11) Use iterated integration to compute

calculus 3 review 2 _gr_125.gif] where calculus 3 review 2 _gr_126.gif]

    Solution. By Fubini's theorem,

calculus 3 review 2 _gr_127.gif]

calculus 3 review 2 _gr_128.gif]

(12) Find the volume of the solid bounded below by the rectangle

calculus 3 review 2 _gr_129.gif]

in the calculus 3 review 2 _gr_130.gif]-plane and above by the graph of calculus 3 review 2 _gr_131.gif]

    Solution. The volume is given by the following double integral and can be compute using Fubini's theorem.
    
calculus 3 review 2 _gr_132.gif]

calculus 3 review 2 _gr_133.gif]
    
calculus 3 review 2 _gr_134.gif]

calculus 3 review 2 _gr_135.gif]

calculus 3 review 2 _gr_136.gif]
calculus 3 review 2 _gr_137.gif]

(13) Sketch the region of integration and write an equivalent integral with the order of integration reversed given calculus 3 review 2 _gr_138.gif]

    Solution. We graph the region:

calculus 3 review 2 _gr_139.gif]

The iterated integral calculus 3 review 2 _gr_140.gif] is with the region as a vertically simple region. Also, calculus 3 review 2 _gr_141.gif] and so calculus 3 review 2 _gr_142.gif] and so

calculus 3 review 2 _gr_143.gif]

calculus 3 review 2 _gr_144.gif]

(14) Find the volume of the solid bounded above by the paraboloid calculus 3 review 2 _gr_145.gif] and below by the plane calculus 3 review 2 _gr_146.gif]

    Solution. The projected region in the calculus 3 review 2 _gr_147.gif]-plane is calculus 3 review 2 _gr_148.gif] which is symmetric about both the calculus 3 review 2 _gr_149.gif]-axis and the calculus 3 review 2 _gr_150.gif]-axis. Thus,

calculus 3 review 2 _gr_151.gif]

calculus 3 review 2 _gr_152.gif]

Cite this as:
Calculus 3 Review 2
Published by Library of Math -- Online math organized by subject into topics.
Written by Smith, David A.
http://www.libraryofmath.com/calculus-3-review-2.html
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