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All Textbook Solutions for Multivariable Calculus

17E18E19E20E21E22E23E24E25E26E27E28E29E30E31E32E33E34E35E36E37E38E39E40E41E42E43E44E45E46E47E48E49E50E51E52E53E54E55E56E57E58E59E60E61E62E63E64E65E66E67E68E69E70E71E72E73E74E75E76E77E78E79E80E81E82E83E84E85E86E87E88E89E90E91E92E93E94E95E96E97E98E99E100E101E102E103E104E105E106E107E108E109E110E111E112E113E114E115E116E117E118E119E120EThink About It Let V be the number of applicants to a university, p the charge for food and housing at the university, and r the tuition. Suppose that .N is a function of p and t such that N/p0 and N/t0. What information is gained by noticing that both partials are negative?Investment The value of an investment of $1000 earning 6% compounded annually is V(I,R)=10001+0.06(1R)1+t10 where t is the annual rate of inflation and R is the tax rate for the person making the investment. Calculate Vt(0.03,0.28) and VR(0.03,0.28). Determine whether the tax rate or the rate of inflation is the greater negative factor in the growth of the investment123EApparent Temperature A measure of how hot weather feels to an average person is the Apparent Temperature Index. A model for this index is A=0.885t22.4h+1.20th0.544 where A is the apparent temperature in degrees Celsius. t is the air temperature, and h is the relative humidity in decimal form. (Source: The UMAP Journal) (a) Find At and Ah when t=30 and h= 0.80. (b) Which has a greater effect on A. air temperature or humidity? Explain.Ideal Gas Law The Ideal Gas Law states that PV=nRT where P is pressure, V is volume, n is the number of moles of gas, R is a fixed constant (the gas constant), and T is absolute temperature. Show that TPPVVT=1126E127E128E129E130E131ECONCEPT CHECK ApproximationDescribe the change in accuracy of dz as an approximation of z as x and y increase.2E3E4EFinding a Total DifferentialIn Exercises 38, find the total differential. z=12(ex2+y2ex2y2)Finding a Total DifferentialIn Exercises 38, find the total differential. z=extany7E8E9E10E11E12EUsing a Differential as an Approximation In Exercises (a) find f (2,1) and f (2.1,1.05) and calculate z , and (b) use the total differential d z to approximate z. f(x,y)=yex14E15E16E17E18E19E20EArea The area of the shaded rectangle in the figure is A=lh The possible errors in the length and height are l and h. respectively. Find dA and identify the regions in the figure whose areas are given by the terms of dA What region represents the di (Terence between A and dA?Volume The volume of the red right circular cylinder in the figure is V=r2h. The possible errors in the radius and the height are r and h. respectively. Find dV and identify the solids in the figure whose volumes are given by the terms of dV. What solid represents the difference between V and dV?23E24E25E26EWind Chill The formula for wind dull C (in degrees Fahrenheit) is given by C=35.74+0.6215T35.75x0.16+0.4275Tv0.16 where v is the wind speed in miles per hour and T is the temperature in degrees Fahrenheit. The wind speed is 233 miles per hour and the temperature is 8+1 to estimate the maximum possible propagated error and relative error in calculating the wind chill. (Source: National Oceanic and Atmospheric Administration)28E29E30EVolume A trough is 16 feet long (see figure). Its cross sections are isosceles triangles with each of the two equal sides measuring 18 inches. The angle between the two equal sides is (a) Write the volume of the trough as a function of and determine die value of such that die volume is a maximum. (b) The maximum error in the linear measurements is one-half inch and die maximum error in the angle measure is? Approximate the change in the maximum volume.32E33E34E35E36E37E38E39E40E1EImplicit Differentiation Why is using the Chain Rule to determine the derivative of the equation F(x,y)=0 implicitly easier than using the method you learned in Section 2.5?Using the Chain Rule In Exercises 3-6, find dw/dt using the appropriate Chain Rule. Evaluate dw/dt at the given value of t Function Value w=x2+5y t=2 x=2t,y=tUsing the Chain Rule In Exercises 3-6, find dw/dt using the appropriate Chain Rule. Evaluate dw/dt at the given value of t Function Value w=x2+y2 t=0 x=cost,y=etUsing the Chain Rule In Exercises 3-6, find dw/dt using the appropriate Chain Rule. Evaluate dw/dt at the given value of t Function Value w=xsiny t=0 x=et,y=tUsing the Chain Rule In Exercises 3-6, find dw/dt using the appropriate Chain Rule. Evaluate dw/dt at the given value of t Function Value w=lnyx t=4 x=cost,y=sintUsing Different Methods In Exercises 7-12, find dw/dt (a) by using the appropriate Chain Rule and (b) by converting w to a function of t before differentiating. w=x1y,x=e2t,y=t3Using Different Methods In Exercises 7-12, find dw/dt (a) by using the appropriate Chain Rule and (b) by converting w to a function of t before differentiating. w=cos(xy),x=t2,y=1Using Different Methods In Exercises 7-12, find dw/dt (a) by using the appropriate Chain Rule and (b) by converting w to a function of t before differentiating. w=x2+y2+z2,x=cost,y=sint,z=etUsing Different Methods In Exercises 7-12, find dw/dt (a) by using the appropriate Chain Rule and (b) by converting w to a function of t before differentiating. w=xycosz,x=t,y=t2,z=arccostUsing Different Methods In Exercises 7-12, find dw/dt (a) by using the appropriate Chain Rule and (b) by converting w to a function of t before differentiating. w=xy+xz+yz,x=t1,y=t21,z=tUsing Different Methods In Exercises 7-12, find dw/dt (a) by using the appropriate Chain Rule and (b) by converting w to a function of t before differentiating. w=xy2+x2z+yz2,x=t2,y=2t,z=2Projectile Motion In Exercises 13 and 14. the parametric equations for the paths of two objects are given. At what rate is the distance between the two objects changing at the given value of t? x1=10cos2t,y1=6sin2tFirstobjectx2=7cost,y2=4sintSecondobjectt=/2Projectile Motion In Exercises 13 and 14. the parametric equations for the paths of two objects are given. At what rate is the distance between the two objects changing at the given value of t? x1=482t,y1=482t16t2Firstobjectx2=483t,y2=48t16t2Secondobjectt=115E16E17E18EUsing Different Methods In Exercises 19-22, find w/ s and w/ t (a) by using the appropriate Chain Rule and (b) by converting w to a function of s and t before differentiating. w=xyz,x=s+t,y=st,x=st2Using Different Methods In Exercises 19-22, find w/ s and w/ t (a) by using the appropriate Chain Rule and (b) by converting w to a function of s and t before differentiating. w=x2+y2+z2,x=tsins,y=tcoss,z=st2Using Different Methods In Exercises 19-22, find w/ s and w/ t (a) by using the appropriate Chain Rule and (b) by converting w to a function of s and t before differentiating. w=zexy,x=st,y=s+t,z=st22EFinding a Derivative ImplicitlyIn Exercises 2326, differentiate implicitly to find dy/dx. x2xy+y2x+y=024EFinding a Derivative Implicitly In Exercises 23-26. differentiate implicitly to Find dy/dx. lnx2+y2+x+y=426E27E28E29E30E31E32E33E34E35E36E37E38EHomogeneous Functions A function f is homogeneous of degree n when f(tx,ty)=tnf(x,y) . In Exercises 39-42, (a) show that the function is homogeneous and determine n , and (b) show that xfx(x,y)+yfy(x,y)=nf(x,y). f(x,y)=2x25xy40E41E42E43E44E45E46E47E48E49E50EMoment of Inertia An annular cylinder has an inside radius of r1, and an outside radius of r2 (see figure). Its moment of inertia is 1=12m(r12+r22) where m is the mass. The two radii are increasing at a rate of 2 centimeters per second. Find the rate at which I is changing at the instant the radii are 6 centimeters and 8 centimeters. (Assume mass is a constant.)Volume and Surface Area The two radii of the frustum of a right circular cone are increasing at a rate of 4 centimeters per minute, and the height is increasing at a rate of 12 centimeters per minute (see figure). Find the rates at which the volume and surface area are changing when the two radii are 15 centimeters and 25 centimeters and the height is 10 centimeters.Cauchy-Riemann Equations Given the functions u(x, y) and v(x, y), verify that the Cauchy-Riemann equations ux=vy and uy=vx can be written in polar coordinate form as ur=1rv and vr=1ruCauchy-Riemann Equations Demonstrate the result of Exercise 53 for the functions u=lnx2+y2andv=arctanyxHomogeneous Function Show that if f(x, y) is homogeneous of degree n, then xfx(x,y)+yfy(x,y)=nf(x,y) [Hint: Let g(t)=f(tx,ty)=tnf(x,y) Find g (t) and then let t=1.]1E2E3E4EFinding a Directional DerivativeIn Exercises 36, use Theorem 13.9 to find the directional derivative of the function at P in the direction of the unit vector u=cosi+sinj. f(x,y)=sin(2x+y),P(0,),=566E7E8E9E10E11E12E13E14E15E16EFinding the Gradient of a FunctionIn Exercises 1520, find the gradient of the function at given point. z=ln(x2y)x4,(2,3)18E19E20E21E22E23E24E25E26E27E28E29E30EUsing Properties of the GradientIn Exercises 2938, find the gradient of the function and the maximum value of the directional derivative at the given point. h(x,y)=xtany,(2,4)32EUsing Properties of the GradientIn Exercises 2938, find the gradient of the function and the maximum value of the directional derivative at the given point. f(x,y)=sinx2y3,(1,)Using Properties of the GradientIn Exercises 2938, find the gradient of the function and the maximum value of the directional derivative at the given point. g(x,y)=lnx2+y23,(1,2)Using Properties of the GradientIn Exercises 2938, find the gradient of the function and the maximum value of the directional derivative at the given point. f(x,y,z)=x2+y2+z2,(1,4,2)36E37E38E39E40E41E42EUsing a FunctionIn Exercises 4346, (a) find the gradient of the function at P, (b) find a unit normal vector to the level curve f(x,y)=c at P, (c) find the tangent line to the level curve f(x,y)=c at P, and (d) sketch the level curve, the unit normal vector, and the tangent line in the xy-plane. f(x,y)=4x2yc=6,P(2,10)44E45E46E47E48E49E50E51E52ETopography The surface of a mountain is modeled by the equation h(x,y)=50000.001x20.004y2. A mountain climber is at the point (500,300,4390). In what direction should the climber move in order to ascend at the greatest rate?54ETemperature The temperature at the point (x,y) on a metal plate is T(x,y)=x/(x2+y2). Find the direction of greatest increase in heat from the point (3,4).56E57E58E59E60E61E62E63E64E65EOcean Floor A team of oceanographers is mapping the ocean floor to assist in the recovery of a sunken ship. Using sonar, they develop the model D=250+30x2+50siny2,0x2,0y2 where D is the depth in meters, and x and y are the distances in kilometers. (a) Use a computer algebra system to graph D. (b) Because the graph in part (a) is showing depth, it is not a map of the ocean floor. How could the model be changed so that the graph of the ocean floor could be obtained? (c) What is the depth of the ship if it is located at the coordinates x=1 and y=0.5? (d) Determine the steepness of the ocean floor in the positive x-direction from the position of the ship. (e) Determine the steepness of the ocean floor in the positive y-direction from the position of the ship. (f) Determine the direction of the greatest rate of change of depth from the position of the ship.67E68ECONCEPT CHECK Tangent VectorConsider a point (x0,y0,z0) on a surface given by F(x,y,z)=0. What is the relationship between F(x0,y0,z0) and any tangent vector v at (x0,y0,z0) ? How do you represent this relationship mathematically?2E3E4E5E6E7E8E9E10E11E12E13E14E15E16E17E18E19E20E21E22E