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Unformatted text preview: Version 099 Homework 11 Gilbert (59825) 1 This printout should have 22 questions. Multiplechoice questions may continue on the next column or page find all choices before answering. The due time is Central time. You are the first students to try out this new system. Please be patient  bugs will occur, but they will be fixed very quickly! Report any bugs to Shane Lewis(gsl@mail.utexas.edu) and send a copy to me. Thanks. 001 10.0 points Use the Chain Rule to find dw dt for w = xe y/z when x = t 2 , y = 7 t, z = 7 + 5 t. 1. dw dt = parenleftBig 2 t x z 5 xy z parenrightBig e y/z 2. dw dt = parenleftBig t x z 7 xy z parenrightBig e y/z 3. dw dt = parenleftBig t + x z + 7 xy z parenrightBig e y/z 4. dw dt = parenleftBig 2 t + x z + 5 xy z 2 parenrightBig e y/z 5. dw dt = parenleftBig t + x z + 7 xy z 2 parenrightBig e y/z 6. dw dt = parenleftBig 2 t x z 5 xy z 2 parenrightBig e y/z correct Explanation: By the Chain Rule for Partial Differentia tion, dw dt = w x dx dt + w y dy dt + w z dz dt . When w = xe y/z when x = t 2 , y = 7 t, z = 7 + 5 t, therefore, dw dt = 2 te y/z x z e y/z 5 xy z 2 e y/z . Consequently, dw dt = parenleftBig 2 t x z 5 xy z 2 parenrightBig e y/z . 002 10.0 points Use partial differentiation and the Chain Rule applied to F ( x, y ) = 0 to determine dy/dx when F ( x, y ) = cos( x 6 y ) xe 3 y = 0 . 1. dy dx = sin( x 6 y ) + e 3 y 6 xe 3 y 3 sin( x 6 y ) 2. dy dx = sin( x 6 y ) 3 e 3 y 3 sin( x 6 y ) 6 xe 3 y 3. dy dx = sin( x 6 y ) + 3 xe 3 y 6 sin( x 6 y ) e 3 y 4. dy dx = sin( x 6 y ) + e 3 y 3 xe 3 y 6 sin( x 6 y ) 5. dy dx = sin( x 6 y ) 3 xe 3 y 3 sin( x 6 y ) 6 e 3 y 6. dy dx = sin( x 6 y ) + e 3 y 6 sin( x 6 y ) 3 xe 3 y correct Explanation: Applying the Chain Rule to both sides of the equation F ( x, y ) = 0, we see that F x dx dx + F y dy dx = F x + F y dy dx = 0 . Thus dy dx = F x F y = F x F y . Version 099 Homework 11 Gilbert (59825) 2 When F ( x, y ) = cos( x 6 y ) xe 3 y = 0 , therefore, dy dx = sin( x 6 y ) e 3 y 6 sin( x 6 y ) 3 xe 3 y . Consequently, dy dx = sin( x 6 y ) + e 3 y 6 sin( x 6 y ) 3 xe 3 y . 003 10.0 points The temperature at a point ( x, y ) in the plane is T ( x, y ) measured in degrees Celsius. If a bug crawls so that its position in the plane after t minutes is given by x = 2 + t, y = 5 + 3 2 t, determine how fast is the temperature rising on the bugs path after 2 minutes when T x (2 , 8) = 20 , T y (2 , 8) = 6 . 1. rate = 15 C / min 2. rate = 17 C / min 3. rate = 14 C / min correct 4. rate = 16 C / min 5. rate = 13 C / min Explanation: By the Chain Rule for partial differentia tion, the rate of change of temperatuure T on the bugs path is given by dT dt = dT ( x ( t ) , y ( t )) dt = T x dx...
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This homework help was uploaded on 03/19/2008 for the course M 408M taught by Professor Gilbert during the Fall '07 term at University of Texas at Austin.
 Fall '07
 Gilbert

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